YouTube transcript (UrRYITjDOww) — Transcript
Full transcript
- 0:02[Music]
- 0:17hello thanks for watching and welcome to
- 0:20the next video in my series on basic
- 0:22statistics now as usual a few things
- 0:25before we get started number one if
- 0:27you're watching this video because you
- 0:28are struggling in a class right now I
- 0:31want you to stay positive and keep your
- 0:33head up if you're watching this it means
- 0:35you've accomplished quite a bit already
- 0:37you're very smart and talented but you
- 0:39may have just hit a temporary rough
- 0:41patch now I know with the right amount
- 0:43of hard work practice and patience you
- 0:46can work through it I have faith in you
- 0:49many other people around you have faith
- 0:51in you so so should you number two
- 0:55please feel free to follow me here on
- 0:57YouTube on Twitter on Google+ or on
- 1:01LinkedIn that way when I upload a new
- 1:03video you know about it and it's always
- 1:06nice to connect with my viewers online
- 1:08I'll feel that life is much too short
- 1:10and the world is much too large for us
- 1:12to miss the chance to connect when we
- 1:14can number three if you like the video
- 1:17please give it a thumbs up share it with
- 1:20classmates or colleagues or put it on a
- 1:22playlist that does encourage me to keep
- 1:24making them for you on the flip side if
- 1:27you think there's something I can do
- 1:28better please leave a con instructive
- 1:30comment below the video and I will take
- 1:32those ideas into account when I make new
- 1:35ones and finally just keep in mind that
- 1:37these videos are meant for individuals
- 1:39who are relatively new to Stats so I'm
- 1:42just going over basic concepts and I
- 1:45will be doing so in a slow deliberate
- 1:48manner not only do I want you to know
- 1:51what is going on but also why and how to
- 1:55apply it so all that being said let's go
- 1:58ahead and get started so this video is
- 2:01part two of our larger video on the
- 2:04one-way analysis of variance or the
- 2:06oneway Innova now in part one we went
- 2:10over an example problem and really sort
- 2:12of took it apart and looked at how all
- 2:14the parts of the oneway and Nova fit
- 2:17together so in part two we're going to
- 2:20go into Microsoft Excel and do a quote
- 2:23hand calculation of the oneway Anova so
- 2:27if you're watching the video on YouTube
- 2:29you can go to the description deson
- 2:30below the video and there you'll find a
- 2:32link to the corresponding blog post for
- 2:35this problem on the blog post you can
- 2:37actually download a blank version of the
- 2:39Excel file we're going to use and you
- 2:41can follow along step by step so without
- 2:44further waiting let's go ahead and get
- 2:46started on part two of the one-way
- 2:49analysis of
- 2:51variance now what we're going to do in
- 2:54Excel is try to replicate the output in
- 2:58SPSS and again SPSS is the statistical
- 3:02software I use in my work so I went
- 3:04ahead and did our example problem in
- 3:07SPSS and this was the result so we're
- 3:10going to go into Excel and actually try
- 3:11to replicate this Anova chart doing hand
- 3:15calculations and of course I don't mean
- 3:17literally by hand we're going to use
- 3:19Excel formulas but in the end we want to
- 3:22have a chart that looks exactly like
- 3:26this now before we actually go into
- 3:28Excel we do have to go over a few
- 3:31formulas for the oneway Inova now I
- 3:34mentioned before that some textbooks and
- 3:36some professors and classes and
- 3:39everything else call the same things by
- 3:42different names so you may have to cross
- 3:45reference what we're going to learn here
- 3:46with how it's presented in your class so
- 3:49you may actually want to have your
- 3:50textbook open or your notes open as we
- 3:53go through it it's the same thing but
- 3:55again they go by different names
- 3:57depending on what text you're using or
- 3:58what Professor you have
- 4:01so before we do that I just want to
- 4:02point out what's going to come up um
- 4:04here in a second when you see the
- 4:06variable in or the large n that
- 4:09represents the total number of
- 4:11observations in our experiment or in our
- 4:14problem in this case it's 21 remember
- 4:18now C is the number of columns we have
- 4:22in our chart remember in this problem we
- 4:24had three because we had three years of
- 4:28students so let's talk about SSC
- 4:31remember that's sum of squares of the
- 4:33columns or sometimes What's called the
- 4:35treatments it's also the levels of our
- 4:38single Factor we're looking at remember
- 4:41I said they can go by different names
- 4:42that's what I mean so in this case we
- 4:44had year one year 2 and year three those
- 4:47are our
- 4:49columns now the SSC also has a degrees
- 4:52of freedom actually all these have their
- 4:54own degrees of freedom in the SSC case
- 4:58the degrees of freedom of the columns is
- 5:02C
- 5:04minus1 now the
- 5:06MSC is the mean squared of the columns
- 5:11so mean square of the columns that's
- 5:15MSC and that is the SSC so the sum of
- 5:18squares of the columns divided by its
- 5:21own degrees of freedom again this is all
- 5:25very abstract until we do it so just
- 5:27hang with me so the SS e is the sum of
- 5:31the squares of the error or the within
- 5:34each column each individual column sum
- 5:37of squares so the SSC is a sum of
- 5:40squares between the columns the SS is a
- 5:43sum of squares within each
- 5:46column so degrees of freedom for SSC is
- 5:50n minus C and again we'll put numbers in
- 5:54all these here in a minute so the MSE is
- 5:58the mean squared error now the MSE is
- 6:02very important in many areas of
- 6:04Statistics so keep that in the back of
- 6:06your head as we proceed but msse is the
- 6:09mean squared of the error and that is
- 6:12the ssse divided by the degrees of
- 6:16freedom for the
- 6:17error and then we have SST which of
- 6:21course is the sum of squares of the
- 6:22total the total sum of squares the
- 6:25degrees of freedom for the SST is in -1
- 6:30so the total number of observations
- 6:34minus1 now in the end we will end up
- 6:37with an F statistic remember way back
- 6:40when in our f-stat video what the f
- 6:42statistic is it's a ratio the F ratio is
- 6:47a ratio of two variances so in our F
- 6:51ratio here in the numerator we're going
- 6:54to have the mean sum of squares for the
- 6:57columns which is the variant
- 7:00between the
- 7:01columns and then in the denominator
- 7:04we're going to have the mean squared
- 7:07error which is the variance of the sum
- 7:09of squares inside the columns so we have
- 7:13between the columns on top and within
- 7:17the columns in the denominator that's
- 7:19why you will often see this as an F
- 7:22ratio that is between divided by Within
- 7:27between the columns divided by the Vari
- 7:30of the data within the
- 7:34columns so let's go ahead and actually
- 7:36put some numbers in here let's find our
- 7:38degrees of freedom first so remember the
- 7:40degrees of freedom for SSC was C the
- 7:43number of columns minus one so in this
- 7:46case it's three because we have three
- 7:47columns minus one which equals 2 so the
- 7:52MSC equals the SSC divided by that
- 7:56degrees of freedom which is of course
- 7:58two
- 8:00now for the
- 8:01SSE the degrees of freedom for the ssse
- 8:04was n minus C so n is 21 that's number
- 8:09of overall observations minus 3 which is
- 8:12the number of columns so that is 18 so
- 8:16our msse equals the ssse divided by that
- 8:20degrees of freedom which is
- 8:2318 now the degrees of freedom total the
- 8:26SST is n minus one so our overall all
- 8:30number of observations minus 1 which of
- 8:32course is 21 - 1 = 20 now our F ratio
- 8:38Remains the Same it is still the msse
- 8:41divided by the
- 8:43MSE now let's go ahead and go into Excel
- 8:46and figure out the SSC and the SS which
- 8:51will allow us to find the MSC in the MSE
- 8:55that we need to do this
- 8:57problem so here we are in in Excel where
- 9:00we're going to do our hand calculation
- 9:02of this Anova problem but before I give
- 9:04you a tour of our spreadsheet here I
- 9:06want to draw your attention to the
- 9:07yellow box up here at the top now
- 9:10remember we're going to need the sum of
- 9:12squares however Excel does not have a
- 9:14sum of squares formula so what we're
- 9:17going to do is we're going to use the
- 9:18variance formulas and then alter them a
- 9:21bit so the Excel variance formulas which
- 9:23is var. S and var. P which is sample
- 9:28variance and population variance do the
- 9:30averaging step we don't want so the
- 9:33sample variance will divide by n minus
- 9:35one and the population variance will
- 9:37divide by n therefore we will have to
- 9:40sort of quote undo that step and make a
- 9:44couple of other adjustments to get the
- 9:45sum of squares we want so in the
- 9:48calculations we do in the formulas we
- 9:50use you will see multiplication added in
- 9:54that is the undoing of the variance
- 9:58averaging and other multiplication
- 10:00that's in the SST the SSC and the SS e
- 10:05so what I'm saying here is that some of
- 10:08this you're just going to have to take
- 10:10on faith and I hate saying something
- 10:12like that in a math video but that's
- 10:14just the way it is I did not go over the
- 10:17individual SST SSC and ssse formulas
- 10:21because I thought your face would glaze
- 10:23over anymore than it already is and you
- 10:25can find those in your books however I
- 10:28will try to point out out what each
- 10:30component is when we put in the formulas
- 10:33okay so that's sort of my little caveat
- 10:35here now on the top left you will see
- 10:37our chart our data as we had it in the
- 10:39PowerPoint portion so we have our year
- 10:41one scores our year 2 scores and our
- 10:44year three scores nothing much surprise
- 10:47there and then we have a column summary
- 10:50so the mean for year 1 year 2 and year
- 10:53three and then we have the overall mean
- 10:55there in the middle now over on the
- 10:58right hand side I just put the formulas
- 11:00for the sample variance and the sum of
- 11:02squares we're going to be doing if
- 11:04you're really not interested in the
- 11:05formulas that much just ignore those two
- 11:08blue boxes up there in the right hand
- 11:11side now if you look below our data
- 11:13you'll see n and C well n remember is
- 11:16going to be the total number of
- 11:17observations we have which in this
- 11:19problem of course will be 21 C is the
- 11:22number of groups or columns or
- 11:24treatments we have so in this problem
- 11:27will be three over on the right you will
- 11:30see the SPSS output for this problem so
- 11:34what we're going to try to do is
- 11:35replicate that little chart over there
- 11:38on the left hand side where we have the
- 11:40green header and then the SSC SSC SST
- 11:43there in that chart so we're going to
- 11:45try to make that chart on the left look
- 11:48like the SPSS output over here on the
- 11:51right and of course we will actually do
- 11:53this problem in Excel using its Anova so
- 11:56we're going to have three versions or
- 11:58three out puts of the exact same thing
- 12:01to make them all match now everything
- 12:03else on here is pretty much a hint so we
- 12:05don't have to go back to PowerPoint to
- 12:07find these formulas So Below there on
- 12:10the left hand side you will see the MSC
- 12:13the msse and the F ratio and again those
- 12:17just come from our slides we already had
- 12:20now in the purple boxes on the lower
- 12:22right those the formulas we're going to
- 12:24use to actually find our sum of squares
- 12:27so I will explain those further when we
- 12:29get to that step but I just wanted to
- 12:31put them here sort of in a text format
- 12:33so you can copy and paste them into the
- 12:36proper cell so let's go ahead and do
- 12:39some actual calculations and put in some
- 12:41data so the first thing we're going to
- 12:43do is we're going to go over to the n
- 12:45and the c boxes over here on the left
- 12:48hand side so this is easy so our n in
- 12:51this case is 21 so we're going to go
- 12:53ahead and put 21
- 12:54there that's the number of observations
- 12:57we have and then C is the number of col
- 12:59which is
- 13:00three so we'll go ahead and do that now
- 13:04the next thing I want to do is find the
- 13:07column means so we'll go up to the year
- 13:10one mean box which is the bottom of the
- 13:12year one scores and then we'll use the
- 13:15average formula so we'll type equals
- 13:19average and I'm actually go ahead and
- 13:21begin filling that out now we'll just
- 13:24select all seven of those scores in the
- 13:27year one column close print
- 13:29parentheses and there we go so this is
- 13:3371.7 which is what we had in the
- 13:35PowerPoint now we need the mean for all
- 13:38three columns so we'll go ahead and do
- 13:39the same thing for year
- 13:45two and we'll go and do the same thing
- 13:47for year three in case you're wondering
- 13:49I don't drag across because it takes the
- 13:50color with it so they would all be blue
- 13:52if I dragged across okay so we have the
- 13:56column mean for each of the student
- 13:59years so 71.7 one for year 1 students
- 14:0375.2 n for year 2 students and 7657 for
- 14:07year three students now we want the
- 14:10overall mean which is in this gray box
- 14:12here below the yellow box so again
- 14:15equals
- 14:17average and then we'll select all 21
- 14:22scores in our data and hit enter so now
- 14:26we have our overall mean of 7
- 14:314.52 so again using Excel we did hand
- 14:34calculations of all three column means
- 14:37and the overall mean which of course we
- 14:38know we need to do this type of problem
- 14:41now let's go ahead and go down to our
- 14:45chart over here on the lower left let's
- 14:47go ahead and find the degrees of freedom
- 14:50for each source of variance so remember
- 14:53we have column variance so between the
- 14:55columns we have within each column
- 14:57variance and then we have the the total
- 15:00sum of squares the total variance okay
- 15:02so remember that for the SSC we can see
- 15:05this sort of over here on the right hand
- 15:06side so degrees of freedom between which
- 15:09is the same thing as SSC is C minus one
- 15:13so we could say equals c which is this
- 15:16cell right here minus
- 15:19one and of course that is two now we
- 15:22need degrees of freedom for within so
- 15:25that is n minus C and you can see that
- 15:28little box on the right to help you sort
- 15:30of cheat a little so equals n which is
- 15:34that cell minus C which is that cell and
- 15:39that gives us 18 degrees of freedom now
- 15:41our total degrees of freedom is n minus
- 15:44one so this going to be equals in that
- 15:47cell minus
- 15:49one and that is 20 so that's very very
- 15:53easy now comes the hard part now we have
- 15:58to find the sum of
- 16:00squares now I went ahead and put
- 16:02placeholders in in our chart over here
- 16:04on the left hand side so we know where
- 16:06everything goes so you look in the SS
- 16:08column we have SSC SS and SST Su of
- 16:13squares column sum of squares erir and
- 16:15some of squares total now on the lower
- 16:18right you will see boxes outlined in
- 16:20sort of a purple color so those the
- 16:23actual formulas we're going to put in
- 16:26each one of those cells so let's take a
- 16:28look at each each one very briefly now
- 16:31there might be some multiplication in
- 16:32here you don't fully understand because
- 16:34I did not go over the actual formulas
- 16:37for SSC ssse and SST because they are
- 16:40mind- numbing you can find them in your
- 16:42book and the way we're doing it you
- 16:44really don't have to worry about it and
- 16:46that just sort of brings up my overall
- 16:48point the chances of you having to do an
- 16:50a Nova by hand are basically zero at
- 16:54least I hope not you're going to be
- 16:55using Excel or
- 16:57SPSS or many tab or whatever else it
- 17:00might be so we're doing all this by hand
- 17:02just so you can see how everything
- 17:03relates not because you'll have to do it
- 17:06that often and hopefully never so let's
- 17:08look at the top one first and that is
- 17:11SSC so in this one I'll go ahead and put
- 17:14my mouse in there you can see that we
- 17:16have SSC equals
- 17:20v.s that is the formula for sample
- 17:24variance and it's going to B sells A10
- 17:28to C10 let's go up here what is A10 and
- 17:32C10 well that is the column means so
- 17:37it's going to look at the variance of
- 17:39those three column
- 17:42means and then we multiply by two but
- 17:45where does the two come from in this
- 17:47case the two comes from the number of
- 17:48columns we have minus one so basically
- 17:52that's the same way of saying it's
- 17:53degrees of freedom so that's where that
- 17:55two comes from where does the seven come
- 17:57from well well that's how many
- 17:59observations we have in each column so
- 18:03v.s is the variance formula the sample
- 18:06variance formula for those three column
- 18:09means time 2 which is number of columns
- 18:12minus one so that's 2 time 7 which is
- 18:16the number of observations in each
- 18:19column so let's go ahead and go over
- 18:22here to our SSC box I'm going to take
- 18:24out the
- 18:25text then I'm going to go over here and
- 18:28copy
- 18:31our text in our box we'll go back over
- 18:33to the
- 18:34SS cell we'll paste it now I'm just
- 18:38going to take out the SSC part so delete
- 18:41delete delete hit
- 18:43enter and there we go so the sum of
- 18:46squares for the columns or the between
- 18:49sum of squares is
- 18:5188.6 67 repeating so let's go ahead and
- 18:55look at the SSE formula and it is
- 18:58admittedly much more involved if we take
- 19:00it apart we can see where everything
- 19:01comes from so we're using the v.s
- 19:04formula again so is the sample variance
- 19:08now the first one asks for cells A2
- 19:11through A8 well what are those well A2
- 19:15through
- 19:16A8 are the data points for column 1 or
- 19:21all the year one scores so we're asking
- 19:23for the sample variance of those seven
- 19:27scores
- 19:28now we're going to multiply by six well
- 19:31why are we multiplying by six well that
- 19:34goes up to the formulas up here at the
- 19:36top the sample variance is n minus one
- 19:38in the denominator well we do not want
- 19:40that we want to undo that so that's why
- 19:42we're multiplying by 7 - 1 which of
- 19:45course is six then we're going to add to
- 19:48that the variance of the next column so
- 19:51B2 through B8 same thing * 6 and then
- 19:55we're going to add that to the variance
- 19:584 three so C2 through C8 so that is all
- 20:02that is it's just the variance of each
- 20:05column added together so we'll go ahead
- 20:08and copy all that well first we'll go
- 20:11over to SSC and delete it make room now
- 20:14we'll go over copy all that contrl c on
- 20:18my PC contrl V to paste it now I'm going
- 20:22to go up and modify it by taking out the
- 20:25SS at the beginning delete now we hit
- 20:28enter
- 20:30and there we have a sum of squares
- 20:32within or an
- 20:34SS of 281
- 20:3712.57 so that is our sum of squares of
- 20:40the within and again that's within the
- 20:42columns we just add them all together
- 20:45now we'll go to SST sum of squares total
- 20:47so we'll delete
- 20:48that now if you look down here in our
- 20:51formula we have SS equal 20 * vs of A2
- 20:58through C8 well what is A2 through C8
- 21:02that's
- 21:03everything so A2 through C8 is our
- 21:07entire data set now we take the variance
- 21:10of that and we multiply it by 20 why
- 21:14well remember our variance is n minus
- 21:16one so we have 21 scores minus one we're
- 21:20going need to undo that put it in the
- 21:21top so that's what we multiply by 20 so
- 21:25we'll go ahead and select all
- 21:27that contrl C to copy we'll go over to
- 21:30our SS column here the SST contrl V to
- 21:34paste we'll take
- 21:36out the SST at the beginning hit enter
- 21:40and there we
- 21:41go now if you look close enough you will
- 21:43see that the
- 21:44SST is the sum of the SS and the SSC so
- 21:5188.6 667 plus 281 12.5 sish when you add
- 21:57those together you will get
- 22:0129123 so that goes back to the idea of
- 22:04partitioning the total variance so our
- 22:07total variance of SST is made up of two
- 22:09components the SS e and the SSC when you
- 22:13add those together you get the SST in
- 22:16return okay so a few more things to do
- 22:19now we need to find the
- 22:21MSC so that's up here under the MS
- 22:25column now if you look down here I have
- 22:27the little formula for the MSC or the
- 22:30mean square of the columns so we're
- 22:32going to delete the text and this is
- 22:34just the SSC divided by the degrees of
- 22:37freedom for columns and we have both of
- 22:39those so this is equal the SSC which we
- 22:43just found which is over here divided by
- 22:46the degrees of freedom for the SSC which
- 22:49is to the left of that so we go ahead
- 22:51and click that cell and hit enter now we
- 22:54have a mean Square for The Columns of 44
- 22:58. 3333 repeating now let's go ahead and
- 23:01do the
- 23:02msse so we'll delete the text in that
- 23:04cell so this is the SS divided by its
- 23:07degrees of freedom so we'll go to that
- 23:09cell we already have selected this is
- 23:12equal the SS the 281
- 23:1612.57 or whatever it was divided by its
- 23:20degrees of freedom which is to the left
- 23:21of it that's 18 and we'll go ahead and
- 23:24hit
- 23:25enter and that is 156
- 23:29257 so now we have our MSC and our MS e
- 23:36now what is f well f is merely division
- 23:40the MSC divided by the MSC of course we
- 23:42have both of those we just did them so
- 23:45the F here equals the
- 23:49MSC which is there to the left divided
- 23:52by the MSE e we found which is there hit
- 23:57enter and you'll notice we
- 24:00have 28 3726 Etc what was it in our SPS
- 24:05output look over here on the right our f
- 24:09is
- 24:11284 same thing so look at the SPSS
- 24:15output over here on the right and our
- 24:17chart we just did over here on the left
- 24:20what do you notice degrees of freedom
- 24:22for the between groups is two degrees of
- 24:25freedom for the within is 18 degrees of
- 24:27freedom to total is 20 the sum of
- 24:30squares for the between 88.6 67 it's in
- 24:34both the within sum of squares was 281
- 24:3812.57 same in both sum of squares total
- 24:432912 38 same in both so in Excel by hand
- 24:49we just replicated the output SPSS gave
- 24:52us so now you can see how everything
- 24:55works together now of course I do admit
- 24:58the only odd part of this are these
- 25:01formulas down here and again you're just
- 25:03going to have to look at them and figure
- 25:05out where everything is being uh pulled
- 25:08from but you're very smart and I know
- 25:09you can do that so let's do one more
- 25:12thing and let actually use excels built
- 25:14in an NOA to see if we get the same
- 25:18thing so we're going to go ahead and go
- 25:20up to data here at the top of the ribbon
- 25:24go all the way over to the right and
- 25:25you'll see data analysis so we'll click
- 25:28on that that now remember we are doing
- 25:31the Anova single Factor so we go and
- 25:34click
- 25:35okay now this wants the input range so
- 25:39we'll select the little icon on the
- 25:40right and then we'll select all of our
- 25:43data actually I'm going to select the
- 25:45column headings to right we'll go back
- 25:49it's grouped by columns we have labels
- 25:52in the first row our Alpha is 05 we're
- 25:55going to stick with that and we'll leave
- 25:57it to new worksheet ply those will give
- 25:59us all of our results on a new worksheet
- 26:02we go a and click
- 26:04okay and here we go so I'm going to go
- 26:06ahead and spread some of these columns
- 26:13out okay now a few things to look
- 26:16at actually a lot to look at so you can
- 26:19see that we have a summary of each score
- 26:22group so year one students year two
- 26:24students and year three students so it
- 26:25gives us our count the sum of all those
- 26:28the average and the variance in each
- 26:31column so we go down to the bottom
- 26:34that's our actual Anova table so you can
- 26:36see our between group sum of squares
- 26:3888.6 667 same thing within groups sum of
- 26:43squares 28 12.57 same thing total sum of
- 26:47squares 29.2 4 same thing degrees of
- 26:51freedom 2 18 and 20 good our mean
- 26:54squares for the with between or the
- 26:57columns for 4 4.33 good are within mean
- 27:01Square
- 27:02156.25 very good divide those we have an
- 27:07F of 2837 Etc same thing we had before
- 27:11now this gives us a few more bits of
- 27:13information which are helpful now
- 27:15remember that when we're doing this sort
- 27:17of problem we're going to test our F
- 27:19value of
- 27:212837 against an F critical value in the
- 27:24F distribution based on our degrees of
- 27:26freedom in the numerator of two
- 27:28and a degrees of freedom of 18 in the
- 27:31denominator with an alpha of 05 we
- 27:34learned how to do that a long time ago
- 27:37so our F critical is
- 27:4135545 so is our F statistic of
- 27:452837 larger or Beyond
- 27:493554 well no so we would fail to reject
- 27:53or null hypothesis that these three
- 27:55means are different so let's go back to
- 27:58our original and you can see that all
- 28:01this is the same now so our SPSS output
- 28:05we set out to replicate we did by hand
- 28:08over here on the left and we did it in
- 28:11Excel using its built-in formula now of
- 28:14course that's the whole point we will
- 28:16not do this by hand we will either use
- 28:17Excel or we'll use some other
- 28:19statistical package but I wanted to show
- 28:21you where all this information comes
- 28:23from so you can understand the
- 28:25foundation sort of the guts the working
- 28:28the gears of the Innova process so let's
- 28:32go ahead and go back into PowerPoint and
- 28:35finish everything
- 28:37up let's go ahead and put in our numbers
- 28:40from Excel so remember in Excel we found
- 28:43that the SSC or the sum of squares and
- 28:46the columns was 88.6 7 then we divide
- 28:51that by our degrees of freedom which is
- 28:53two and we end up with an MSC of 44
- 28:5933 now the MSE e is the
- 29:03SS ided 18 so that was
- 29:0828125 7 ided 18 and that comes out to an
- 29:13MSE of
- 29:16156.25
- 29:18so remember our F ratio here is the msse
- 29:22divided by the
- 29:23MSE so the mean square of the columns
- 29:27divided by thean mean square of the
- 29:29error or you can think of it as the mean
- 29:31Square between divided by the mean
- 29:34Square within so that is 44.3 3 divid
- 29:39156.25 and we end up with an F statistic
- 29:43of
- 29:450.28 and that is exactly what SPSS gave
- 29:48us and what excel's own builtin and Nova
- 29:52calculator gave us as well so we know we
- 29:54did it
- 29:56correctly now how do we we ultimately
- 29:58interpret this so our F ratio is the MSC
- 30:02the MSC that's what we just did now in
- 30:06the numerator we have a degrees of
- 30:07freedom of Two And in the denominator we
- 30:10have a degrees of freedom of 18 so
- 30:13remember when we look up a critical
- 30:15value in the F distribution we have a
- 30:18numerator degrees of freedom and a
- 30:20denominator degrees of freedom and in
- 30:22this case those two degrees of freedoms
- 30:25come from our formulas for the MSC
- 30:28and the m
- 30:30e so we can write this F statistic we
- 30:33got to find like this so we have an
- 30:36alpha level say
- 30:3805 then we have degrees of freedom of C
- 30:42of the columns and a degrees of freedom
- 30:44for the error E so that is the degrees
- 30:47of freedom in the numerator and the
- 30:49degrees of freedom in the denominator so
- 30:51we could write it like this so we need
- 30:53to find the critical value of f with an
- 30:55alpha of
- 30:5605 a numor gra of freedom of Two and a
- 31:00denominator gra of freedom of 18 and we
- 31:02already learned how to do that in a
- 31:04previous video now the easiest way is to
- 31:06go into Excel and use the
- 31:10f.v. RT function that's the F
- 31:13distribution the inverse right tailed
- 31:15that's what all that stands for and we
- 31:17put in those three parameters so an
- 31:20alpha of 05 a numerator degrees of
- 31:23freedom of Two and a denominator degrees
- 31:25of freedom of 18 so when we put that
- 31:28into an Excel cell we will get an F
- 31:31critical value of
- 31:363.55 so we have to ask oursel is the F
- 31:39statistic in our Anova table larger than
- 31:42our F critical value well no so remember
- 31:47what our no hypothesis said we talked
- 31:48about this in the first Anova video and
- 31:51these type of problems our no hypothesis
- 31:53is that the means are equal to each
- 31:56other or that's another way of saying
- 31:58that the means the three means come from
- 32:00a common
- 32:01population so since our F statistic is
- 32:04so low and does not exceed the
- 32:06f-critical value we fail to reject our
- 32:10null
- 32:11hypothesis so we found no significant
- 32:14difference in mean test score by year of
- 32:17student so the means of the firste
- 32:20students the seconde students and the
- 32:22third year students on their study
- 32:24skills exam did not differ significantly
- 32:27and that's
- 32:29it so remember up to this point we could
- 32:33only do comparisons involving two
- 32:35populations independent samples T Test
- 32:37and match sample T Test limiting
- 32:40ourselves to those two comparisons is of
- 32:42course limiting what if we wanted to
- 32:45compare the means of more than two
- 32:46populations like we did in this problem
- 32:49what if we wanted to compare the
- 32:50populations each containing several
- 32:52levels or subgroups so this get hints at
- 32:55the two-way Inova so imagine this
- 32:57scenario where we have year one students
- 33:01year two students and year three
- 33:04students but on the other axis we divide
- 33:07them into male and
- 33:09female now we have two factors so our
- 33:13first factor is the year of the student
- 33:15and our second factor is their
- 33:17biological sex that would be a two-way
- 33:20Anova and we can do that of course using
- 33:22this technique so the analysis of
- 33:25variance is the tool we use to do those
- 33:28more complex
- 33:31analyses okay so that wraps up part two
- 33:34of our video on the oneway Anova or the
- 33:36one-way analysis of variance now I know
- 33:39it was a lot to digest but I really
- 33:42wanted to take you from the very basic
- 33:43conceptual foundations up through an
- 33:46example problem so you can see how all
- 33:47the data is related to each other learn
- 33:49how to do the sum of squares and then
- 33:51eventually find a relationship between
- 33:54those sum of squares because that is the
- 33:55foundation of how we conduct
- 33:58the Inova so I have no doubt that you
- 34:00may need to go back and watch parts of
- 34:01the video to really grasp it but
- 34:03hopefully after watching it you have a
- 34:05really good solid understanding of what
- 34:08an NOA is so a few reminders and then
- 34:11we're done if you're watching the video
- 34:12CU you're struggling in a class stay
- 34:15positive and keep your head up you're an
- 34:17amazing smart talented person never let
- 34:20anyone tell you any differently
- 34:22including yourself if you like the video
- 34:25please give it a thumbs up share it with
- 34:27class mates or colleagues or put it on
- 34:29the playlist feel free to follow me here
- 34:31on YouTube on Twitter on Google+ or on
- 34:35LinkedIn it's always nice hearing from
- 34:38you and finally just keep in mind that
- 34:40the fact that you're on here trying to
- 34:41learn committing yourself to improving
- 34:44as a student or as a business person
- 34:47that is what really matters I firmly
- 34:50believe if you have the right learning
- 34:52process in place the results will take
- 34:55care of themselves so thank you very
- 34:57much for watching
- 34:58I wish you the best of luck in your
- 34:59studies and in your work and I look
- 35:01forward to seeing you again next time
- 35:05[Music]
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