XYZ Mat 120 Module 1 Lesson 1 5 Part 2 — Transcript

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1. 0:00this is module 1 lesson 1.5
2. 0:03part 2. we've already talked about
3. 0:06finding the mean and the
4. 0:10median and the mode and now we're going
5. 0:13to look at
6. 0:14the measure of center for a frequency
7. 0:17distribution
8. 0:18now we talked about frequency
9. 0:19distributions earlier
10. 0:21a frequency distribution remember we
11. 0:23break our data into classes
12. 0:25and then we have our frequency so this
13. 0:27is a little bit different when we're
14. 0:28trying to find the mean
15. 0:30so what we want to do is we want to
16. 0:33start off
17. 0:34by i'm highlighting l1 i'm pressing
18. 0:38clear and i'm pressing enter
19. 0:40in the l1 first list
20. 0:43we want to put our midpoints so the
21. 0:46midpoint between 40 and 44
22. 0:48is 42. the midpoint between 45 and 49
23. 0:53is 47. so i have listed
24. 0:56all of the midpoints that i'm going to
25. 0:58put in this data set
26. 1:03and that will all go into l1
27. 1:09then in l2 so use your arrow go over to
28. 1:12l2
29. 1:13we want to put our frequencies so
30. 1:15they've listed the frequencies
31. 1:17and so you don't have to change anything
32. 1:18you just put the frequencies as you see
33. 1:20them
34. 1:21in your data set even the 0
35. 1:26goes in there and so now what we want to
36. 1:29do
37. 1:30is we've got information in both l1 and
38. 1:32l2 we'll go back to stat
39. 1:34we'll go over to calc at this point
40. 1:37the list is l1 that's good
41. 1:40the frequency list is l2 i'm going to
42. 1:44hit
43. 1:44second 2 because the little l2 is down
44. 1:48here it highlighted in blue
45. 1:50so i need to tell my calculator to read
46. 1:54l1 and l2 we'll calculate
47. 1:57and then we'll hit enter so the first
48. 2:00question is what is the mode
49. 2:02well the mode is not displayed on my
50. 2:04calculator
51. 2:05but i can see from the frequencies
52. 2:08right here
53. 2:14we have 19 this is not working
54. 2:19and so 19 is the most
55. 2:23for my frequencies and we will use
56. 2:27the 47 because the midpoint for the
57. 2:30highest frequency would be 47 but
58. 2:34for my median i can find so go back to
59. 2:36my calculator i'm going to scroll down
60. 2:38my median is going to be 52.
61. 2:41we see that when we scroll down
62. 2:44right here and then we're asked to find
63. 2:48the mean so i'll go back up here and
64. 2:49remember the mean i'm going to just use
65. 2:51my little arrow to go back
66. 2:53is at the very top we have 52.71 so
67. 2:58let's just do 52.7
68. 3:06and so there you have a frequency
69. 3:09distribution
70. 3:10with information in both l1 and l2
71. 3:14now let's do one more like this these
72. 3:17are from your homework so we'll go back
73. 3:19to stat
74. 3:20we'll hit enter to clear i'm going to
75. 3:23do my arrow clear enter
76. 3:26and then go back over here highlight l1
77. 3:28clear
78. 3:29enter and both of my lists are clear so
79. 3:32my data this time it's not classes
80. 3:36it's just data but
81. 3:39we have frequencies and so
82. 3:43we will put the first group in l1
83. 3:46frequency in l2
84. 3:53and then we're going to do the same
85. 3:54thing that we did when we had a
86. 3:56frequency distribution so we'll go back
87. 3:57to stat we'll go over to calc and then
88. 4:00when we hit enter
89. 4:01make sure l1 is your list l2
90. 4:04make sure that's in your frequency
91. 4:07calculate
92. 4:09and the mean is the first thing you see
93. 4:1241.45
94. 4:14so 41.45
95. 4:18they might want you to round that to
96. 4:2141.5
97. 4:22one more data value then your decimals
98. 4:25you
99. 4:26have whole numbers so we want to go one
100. 4:27more decimal place
101. 4:29the median we can scroll down to
102. 4:32c is 42.
103. 4:36and then the mode well the mode is the
104. 4:38one that occurs the most so if i look up
105. 4:40here at my frequencies
106. 4:4343 occurs eight times so my mode
107. 4:46would be 43 because it's the one that
108. 4:49occurs
109. 4:50the most then let's do a problem with
110. 4:54weighting your spanish class your final
111. 4:56grade is based on four categories the
112. 4:58categories are tests
113. 4:59labs homework assignments and a final
114. 5:01exam let's look for a weighted average
115. 5:04for the scores earned in the categories
116. 5:06for these weights so suppose you earned
117. 5:09a 65
118. 5:10on test an 84 on labs a 71 percent on
119. 5:13homework and a 57
120. 5:15on your final exam well here are your
121. 5:17weights
122. 5:18now that happens for this course and all
123. 5:21courses that you take
124. 5:22everything you do is waited a little bit
125. 5:24differently so you can always figure out
126. 5:27what your grades are at any point in
127. 5:29time
128. 5:29if you know what percentages each of
129. 5:32them
130. 5:32count so i'm going to go clear
131. 5:37clear so in l1 i want to put my grades
132. 5:41i got a 65 on my test i got an 84
133. 5:44on labs i got a 71 on homework
134. 5:48and i got a 57 on the exam now let's go
135. 5:52over here and let's put our weights
136. 5:5426 percent is the weight for the test
137. 5:5820 percent is the weight for the labs
138. 6:025 that's .05 is the weight for the
139. 6:06homework and the final exam carries a
140. 6:08lot of weight at 49
141. 6:11so i'm putting those in as decimals and
142. 6:14then i want to do the same thing that i
143. 6:15did before
144. 6:17stat calc make sure
145. 6:20l1 is your list your frequency list is
146. 6:22l2
147. 6:24when we calculate that the course
148. 6:26average is your mean which is 65.18
149. 6:30and that makes sense because your final
150. 6:32exam you made a 57
151. 6:34and it carried 49 of the weight
152. 6:38therefore if you made a 57 on your exam
153. 6:41even though your grades are a little bit
154. 6:42higher here it's not going to
155. 6:45help you a whole lot so having a 65.18
156. 6:49does make sense that that would be your
157. 6:51mean
158. 6:52or your score and then the last thing
159. 6:55you're going to have to do on your
160. 6:56homework is compare your mean median and
161. 6:58mode
162. 6:59and so here are some shapes remember we
163. 7:02talked about this one
164. 7:03this one is positively skewed because
165. 7:07we've got more information to the right
166. 7:09this one is
167. 7:10negatively skewed because we have more
168. 7:12information to the left
169. 7:14and then this one is pretty much
170. 7:15symmetrical so this one
171. 7:18we would say that our mean median and
172. 7:19mode are the same mode remember is the
173. 7:22most
174. 7:23the median is the one in the center and
175. 7:26the mean is your average
176. 7:27so for this one the mean median and mode
177. 7:29are the same but go back over here
178. 7:31remember mode is the most so the
179. 7:35mode is less than the median which is
180. 7:38less than
181. 7:39the mean so the mode is a smaller number
182. 7:42it's to the left it's negative
183. 7:442. and then the median kind of in the
184. 7:47center
185. 7:48over here and then the mean well we've
186. 7:50got a lot of data values if you add up
187. 7:52all these data values you're going to
188. 7:54get
189. 7:54a higher number whereas this one
190. 7:58the mean you got more data values over
191. 8:00here so the mean is less than the median
192. 8:02which is right here in the center which
193. 8:03is less than the mode so the mode
194. 8:05is the highest one so
195. 8:08when you have it like this this mode is
196. 8:10the smallest because it's to the left
197. 8:12and what i'm looking at is i'm looking
198. 8:14at these data values whereas this one
199. 8:16this mode is right in here so those data
200. 8:18values are actually higher