XYZ Mat 120 Module 1 Lesson 1 — Transcript

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1. 0:00this is module 1 lesson 1.1
2. 0:04we're talking about populations and
3. 0:06samples
4. 0:08so let's start off with the definition
5. 0:11of a population
6. 0:12a population is all subjects to be
7. 0:15studied
8. 0:16now a lot of times we think of
9. 0:17populations as being really big
10. 0:19they don't have to be really big the
11. 0:21bigger they are the better
12. 0:23in terms of accuracy of your data but
13. 0:25the population
14. 0:27is the the total group whereas a sample
15. 0:31is members selected from a population so
16. 0:34a sample is a subset
17. 0:36from a population for example
18. 0:39a population could be all students in
19. 0:42this statistics class so
20. 0:44population would be everybody in the
21. 0:45statistics class and the sample would be
22. 0:48a subgroup of that
23. 0:49we could select five students from the
24. 0:51class to answer a question
25. 0:53so when you break down a population into
26. 0:56a smaller group
27. 0:57then that would be your sample another
28. 1:00example
29. 1:01a population is all of the passengers on
30. 1:03an airplane
31. 1:04and a sample would be passengers and
32. 1:07seats one through ten
33. 1:09so there was the sample then is a subset
34. 1:13of my population
35. 1:16a parameter and a statistic a parameter
36. 1:20is a numerical measurement that
37. 1:22describes the characteristics of a
38. 1:24population
39. 1:26so it's got to be something numerical
40. 1:27for instance 40 percent of this class is
41. 1:30over 40 years old so the numerical
42. 1:32measurement is 40 percent
43. 1:3440 is over 40 years old a statistic
44. 1:38is also a numerical measurement but it
45. 1:41describes
46. 1:42characteristics of a sample for example
47. 1:45three of the male students in this class
48. 1:48have blue eyes
49. 1:49so the sample would be students in the
50. 1:51class and we're just picking out three
51. 1:53of them that have blue eyes
52. 1:55so how can we distinguish the
53. 1:57description of a parameter
54. 2:00or a statistic well a parameter is a
55. 2:03numerical measurement that describes a
56. 2:05population
57. 2:06a p and a p a statistic
58. 2:10is a numerical measurement that
59. 2:11describes a sample
60. 2:13so an s and an s so it makes it real
61. 2:17easy to determine
62. 2:18am i looking at a parameter or a
63. 2:20statistic the first question
64. 2:22is are you looking at a sample or a
65. 2:24population
66. 2:26for instance here's an example from your
67. 2:28homework a political scientist surveys
68. 2:3122 of the current 130 representatives
69. 2:36in the state's legislature what is the
70. 2:38size of the sample
71. 2:40well the sample is obviously the
72. 2:41subgroup so we're picking
73. 2:4322 and the population
74. 2:46is the total amount which would be 130.
75. 2:50so the population is always larger
76. 2:53in example 2. us political scientist
77. 2:56surveys 28 of the current 74
78. 2:58representatives
79. 2:59the sample is 28
80. 3:03the total which is the population is 74.
81. 3:06so that should be very easy to identify
82. 3:09now the next question is parameter
83. 3:13or statistic a sample of men
84. 3:19reveals 60 to calculus a
85. 3:22sample remember describes a statistic
86. 3:26determine whether we have a parameter or
87. 3:28statistic for number two
88. 3:3043.85 of voters turned out
89. 3:34in the elections the 2016 elections
90. 3:37so we're looking at all of the elections
91. 3:4143.87 percent of voters we didn't break
92. 3:44that down in any way
93. 3:45so that describes a population therefore
94. 3:4943.87 is a parameter
95. 3:54another homework problem the
96. 3:57the question is to determine whether
97. 3:59it's a parameter or a statistic
98. 4:02two-thirds of the freshman class
99. 4:05two-thirds of the class are freshmen
100. 4:08two-thirds of the class are freshmen
101. 4:12so we're looking at a class so the class
102. 4:16is our population two-thirds
103. 4:19would describe that population so that
104. 4:21would be a parameter
105. 4:23b in a weight loss research study
106. 4:26the sample of 50 men
107. 4:29lost an average of 2.5 pounds sample
108. 4:33right there is a key word
109. 4:35so we're looking at the sample so that
110. 4:37would be a statistic
111. 4:42and then using consumer reports
112. 4:45again a random sample of new cars
113. 4:49gave an average mpg 30.5
114. 4:53so since it's a sample that would be a
115. 4:55statistic
116. 4:58and then the next one facebook tested
117. 5:01the mean amount of time its users
118. 5:03used the site each day and they found
119. 5:05the mean amount of time of
120. 5:06all users on the site
121. 5:10is 80 minutes per day so we're not
122. 5:12breaking down to a sample
123. 5:14we're just looking at the all the users
124. 5:16on the site
125. 5:17so we're looking at the population so
126. 5:19this would be a parameter
127. 5:22so population the numerical description
128. 5:25is
129. 5:25defined as a parameter for a sample it's
130. 5:28a statistic you don't always see the
131. 5:30word sample
132. 5:31but a lot of times you do and then
133. 5:34matching
134. 5:35all right so let's figure this one out
135. 5:37suppose you want to estimate the
136. 5:38percentage of people who got a flu
137. 5:39vaccine who did not get the flu
138. 5:41you take a sample of 100 people who got
139. 5:43the flu vaccine
140. 5:45all right so we want to know about
141. 5:48all of these different descriptions
142. 5:50whether or not the vaccine
143. 5:52worked well whether or not it worked
144. 5:55that is not a sample it's not a
145. 5:57parameter
146. 5:58um it's not an individual it's not a
147. 6:00statistic it's not a population so it's
148. 6:02just a variable did it work
149. 6:03so that one would be c the percentage of
150. 6:07all people who got the flu vaccine
151. 6:11who did not get the flu so the
152. 6:14percentage of the people
153. 6:16so the percentage of all the people who
154. 6:18got the vaccine
155. 6:20so that percentage is going to be
156. 6:23a parameter because we're looking at the
157. 6:25population
158. 6:27of all of those who got the vaccine and
159. 6:30then the percentage of a hundred people
160. 6:32who got the vaccine who did not get the
161. 6:33flu so we're taking a sample we're
162. 6:35taking only 100 people
163. 6:36as compared to all people so that makes
164. 6:39this one a statistic
165. 6:42and then a person who got the flu
166. 6:45vaccine well we're just talking about an
167. 6:46individual if we're just talking about
168. 6:48a person all people who got the vaccine
169. 6:53well
170. 6:53all people is our population and then a
171. 6:56hundred people that's our sample
172. 6:59and so that would be the way we would
173. 7:00answer that