Sampling Techniques
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Statistics and Parameters
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[{"Name":"Sampling Techniques","TopicPlaylistFirstVideoID":0,"Duration":null,"Videos":[{"Watched":false,"Name":"Populations and Samples","Duration":"2m 21s","ChapterTopicVideoID":13106,"CourseChapterTopicPlaylistID":64528,"HasSubtitles":true,"VideoComments":[],"Subtitles":[{"Start":"00:00.110 ","End":"00:05.730","Text":"In this video, we\u0027ll talk about the difference between populations and samples."},{"Start":"00:05.730 ","End":"00:10.125","Text":"Let\u0027s suppose you\u0027re a lobbyist and you\u0027re interested in support"},{"Start":"00:10.125 ","End":"00:16.230","Text":"among people aged 25-40 from California for affirmative action."},{"Start":"00:16.230 ","End":"00:18.420","Text":"In this case,"},{"Start":"00:18.420 ","End":"00:25.300","Text":"the population of your study is all people aged 25-40 in California."},{"Start":"00:26.180 ","End":"00:30.890","Text":"I\u0027ve put the word all in capital letters because I think"},{"Start":"00:30.890 ","End":"00:34.850","Text":"that\u0027s a good clue for knowing what the population is."},{"Start":"00:34.850 ","End":"00:40.579","Text":"It\u0027s all people aged 25-40 in California for this example."},{"Start":"00:40.579 ","End":"00:44.630","Text":"In general, a population is a well-defined collection of individuals,"},{"Start":"00:44.630 ","End":"00:47.225","Text":"or might be objects."},{"Start":"00:47.225 ","End":"00:49.790","Text":"It would be impractical, inefficient,"},{"Start":"00:49.790 ","End":"00:54.715","Text":"and probably impossible to survey all people aged 25-40 in California."},{"Start":"00:54.715 ","End":"00:57.450","Text":"What we would do instead,"},{"Start":"00:57.450 ","End":"00:59.760","Text":"we want to study this population."},{"Start":"00:59.760 ","End":"01:03.008","Text":"But what we do is we take what\u0027s called a sample"},{"Start":"01:03.008 ","End":"01:07.095","Text":"which is going to be a subset of the population."},{"Start":"01:07.095 ","End":"01:12.970","Text":"Your population is some big group,"},{"Start":"01:12.970 ","End":"01:15.680","Text":"in this case, all people aged 25-40,"},{"Start":"01:15.680 ","End":"01:19.435","Text":"and then your sample is a subset of that population."},{"Start":"01:19.435 ","End":"01:25.385","Text":"Usually, we denote the size of the population with a capital letter N,"},{"Start":"01:25.385 ","End":"01:29.870","Text":"and we denote the size of the sample with a lowercase"},{"Start":"01:29.870 ","End":"01:35.630","Text":"n. The sample is always a subset of the population."},{"Start":"01:35.630 ","End":"01:43.180","Text":"In this example, we would take some sample of some people aged 25-40 in California."},{"Start":"01:43.180 ","End":"01:48.500","Text":"Then, what we would do is we would study this group of people."},{"Start":"01:48.500 ","End":"01:49.699","Text":"You would survey them,"},{"Start":"01:49.699 ","End":"01:52.010","Text":"ask them about whether or not they support"},{"Start":"01:52.010 ","End":"01:55.220","Text":"affirmative action and we would use the results of"},{"Start":"01:55.220 ","End":"02:02.630","Text":"the sample to make what\u0027s called statistical inference."},{"Start":"02:02.630 ","End":"02:07.580","Text":"What that means is we\u0027re going to use statistics from"},{"Start":"02:07.580 ","End":"02:13.355","Text":"the sample to form hypotheses about the population."},{"Start":"02:13.355 ","End":"02:19.960","Text":"Next up, we\u0027re going to look at techniques for creating those samples."},{"Start":"02:19.960 ","End":"02:22.250","Text":"Ta-da. We\u0027re done."}],"Thumbnail":null,"ID":13581},{"Watched":false,"Name":"Sampling Techniques","Duration":"4m 43s","ChapterTopicVideoID":13107,"CourseChapterTopicPlaylistID":64528,"HasSubtitles":true,"VideoComments":[],"Subtitles":[{"Start":"00:00.500 ","End":"00:05.880","Text":"In this video, we\u0027re going to talk about 4 different sampling techniques."},{"Start":"00:05.880 ","End":"00:10.650","Text":"The first technique is called simple random sampling."},{"Start":"00:10.650 ","End":"00:12.660","Text":"With the simple random sample,"},{"Start":"00:12.660 ","End":"00:14.760","Text":"that means that everyone in"},{"Start":"00:14.760 ","End":"00:19.065","Text":"the population has an equal chance of being included in the sample."},{"Start":"00:19.065 ","End":"00:22.140","Text":"Let\u0027s say your study, for instance,"},{"Start":"00:22.140 ","End":"00:28.305","Text":"is studying all students at a large high school."},{"Start":"00:28.305 ","End":"00:32.400","Text":"You assign a random number to every student in the high school,"},{"Start":"00:32.400 ","End":"00:35.115","Text":"and then you choose 10 random numbers and"},{"Start":"00:35.115 ","End":"00:38.070","Text":"whoever\u0027s names are attached to those 10 random numbers,"},{"Start":"00:38.070 ","End":"00:40.165","Text":"that forms your sample."},{"Start":"00:40.165 ","End":"00:43.595","Text":"Because every student at the school got a random number,"},{"Start":"00:43.595 ","End":"00:46.130","Text":"each person had an equal chance of being included in"},{"Start":"00:46.130 ","End":"00:49.565","Text":"the sample and so that\u0027s called a simple random sample."},{"Start":"00:49.565 ","End":"00:54.980","Text":"Another random sample is known as a stratified random sample."},{"Start":"00:54.980 ","End":"00:57.020","Text":"Let\u0027s just go with that same example."},{"Start":"00:57.020 ","End":"01:04.300","Text":"Suppose we were studying TV watching habits of students at a large high school."},{"Start":"01:04.300 ","End":"01:10.925","Text":"Instead of sampling using a simple random sample like the way we just talked about,"},{"Start":"01:10.925 ","End":"01:14.059","Text":"this time suppose we want to have in our sample"},{"Start":"01:14.059 ","End":"01:18.020","Text":"equal numbers of people from all 4 classes."},{"Start":"01:18.020 ","End":"01:19.490","Text":"We want 9th graders,"},{"Start":"01:19.490 ","End":"01:22.570","Text":"10th graders, 11th graders, 12th graders."},{"Start":"01:22.570 ","End":"01:29.300","Text":"As soon as we think about the population according to these 4 stratifications,"},{"Start":"01:29.300 ","End":"01:32.150","Text":"then now we would do"},{"Start":"01:32.150 ","End":"01:38.330","Text":"a random sampling in each of the grade levels using the same process as we did before."},{"Start":"01:38.330 ","End":"01:41.850","Text":"Let\u0027s say we took 5 9th graders at random,"},{"Start":"01:41.850 ","End":"01:44.070","Text":"5 10th graders, 5 11th graders,"},{"Start":"01:44.070 ","End":"01:45.515","Text":"and 5 12th graders."},{"Start":"01:45.515 ","End":"01:48.560","Text":"Now we can be sure that in our sample of 20 people,"},{"Start":"01:48.560 ","End":"01:51.770","Text":"we have an equal number from each of the stratifications,"},{"Start":"01:51.770 ","End":"01:56.540","Text":"each of the grade levels and we\u0027ve got randomness within those stratifications."},{"Start":"01:56.540 ","End":"02:00.100","Text":"That would be called a stratified random sample."},{"Start":"02:00.100 ","End":"02:06.620","Text":"Our next type of sampling technique is a clustered random sample."},{"Start":"02:06.620 ","End":"02:11.309","Text":"For this technique, I\u0027m going to give you a different example."},{"Start":"02:11.350 ","End":"02:16.460","Text":"Suppose this time we\u0027re interested in studying whether"},{"Start":"02:16.460 ","End":"02:23.420","Text":"all college students across the entire state of New York, have health insurance."},{"Start":"02:23.420 ","End":"02:26.600","Text":"Now if we were doing a simple random sample,"},{"Start":"02:26.600 ","End":"02:32.750","Text":"we might sample college students across the state and survey them about health insurance."},{"Start":"02:32.750 ","End":"02:34.955","Text":"But suppose we do it differently."},{"Start":"02:34.955 ","End":"02:38.180","Text":"Suppose we look at all of"},{"Start":"02:38.180 ","End":"02:44.060","Text":"the college campuses across the whole state of New York and first sample,"},{"Start":"02:44.060 ","End":"02:47.950","Text":"let\u0027s say 10 colleges at random."},{"Start":"02:47.950 ","End":"02:51.545","Text":"Then at those 10 colleges,"},{"Start":"02:51.545 ","End":"02:56.720","Text":"we go ahead and we get more random samples from within those 10 colleges."},{"Start":"02:56.720 ","End":"03:02.465","Text":"Maybe we ask all the students at those 10 colleges or we do something further."},{"Start":"03:02.465 ","End":"03:07.790","Text":"But what\u0027s different here is that our first step is we are sampling"},{"Start":"03:07.790 ","End":"03:13.255","Text":"10 colleges from all the colleges and those 10 colleges are our clusters."},{"Start":"03:13.255 ","End":"03:16.415","Text":"This is a clustered random sample."},{"Start":"03:16.415 ","End":"03:19.100","Text":"This is different from the stratified."},{"Start":"03:19.100 ","End":"03:20.840","Text":"Some of you may be saying, \u0027\u0027Wait a second,"},{"Start":"03:20.840 ","End":"03:23.576","Text":"this is just like what we did right above.\u0027\u0027"},{"Start":"03:23.576 ","End":"03:26.420","Text":"No, in the stratified random sample,"},{"Start":"03:26.420 ","End":"03:31.160","Text":"we divided up our population into stratifications,"},{"Start":"03:31.160 ","End":"03:35.030","Text":"and then we sampled from all of the stratifications."},{"Start":"03:35.030 ","End":"03:37.970","Text":"Here, we\u0027re taking the population, let\u0027s say,"},{"Start":"03:37.970 ","End":"03:40.850","Text":"I don\u0027t know how many colleges there are in New York, but lots,"},{"Start":"03:40.850 ","End":"03:44.180","Text":"let\u0027s say a couple of a 100 different colleges across the whole state."},{"Start":"03:44.180 ","End":"03:50.910","Text":"We\u0027re first sampling 10 colleges from those 200 and we\u0027re ignoring the rest of them."},{"Start":"03:50.910 ","End":"03:55.009","Text":"We\u0027re using then those 10 colleges to form our sample."},{"Start":"03:55.009 ","End":"04:00.540","Text":"This is different and this is called a clustered random sample."},{"Start":"04:00.920 ","End":"04:04.010","Text":"Now for our last type,"},{"Start":"04:04.010 ","End":"04:07.610","Text":"we\u0027re going to talk here about a convenience sample."},{"Start":"04:07.610 ","End":"04:11.918","Text":"This 1, the name tells all."},{"Start":"04:11.918 ","End":"04:14.600","Text":"Convenience sample is not random."},{"Start":"04:14.600 ","End":"04:19.195","Text":"It\u0027s when you sample people who are easy to reach."},{"Start":"04:19.195 ","End":"04:25.460","Text":"Suppose you\u0027re running for office and you decide that you\u0027re just going to survey"},{"Start":"04:25.460 ","End":"04:27.650","Text":"people who live in"},{"Start":"04:27.650 ","End":"04:29.220","Text":"your neighborhood and then you go around and you"},{"Start":"04:29.220 ","End":"04:31.580","Text":"survey all the people right in your neighborhood."},{"Start":"04:31.580 ","End":"04:33.620","Text":"There\u0027s nothing random about that."},{"Start":"04:33.620 ","End":"04:36.200","Text":"You went there because it was easy to reach because it\u0027s"},{"Start":"04:36.200 ","End":"04:41.105","Text":"your neighborhood and that is called a convenience sample."},{"Start":"04:41.105 ","End":"04:44.220","Text":"That\u0027s it, ta-da, we\u0027re done."}],"Thumbnail":null,"ID":13582},{"Watched":false,"Name":"Exercise 1","Duration":"54s","ChapterTopicVideoID":13102,"CourseChapterTopicPlaylistID":64528,"HasSubtitles":true,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:05.220","Text":"A college is interested in studying depression among their first-year students."},{"Start":"00:05.220 ","End":"00:10.125","Text":"They choose 25 students from the entire cohort at random to survey."},{"Start":"00:10.125 ","End":"00:12.450","Text":"What is the study\u0027s population?"},{"Start":"00:12.450 ","End":"00:15.060","Text":"What sampling technique was used?"},{"Start":"00:15.060 ","End":"00:22.500","Text":"The study\u0027s population is all of the first-year students at this college."},{"Start":"00:22.500 ","End":"00:29.480","Text":"Now they tell us that they chose 25 students from the entire cohort at random."},{"Start":"00:29.480 ","End":"00:36.040","Text":"This is a good example of a simple random sample."},{"Start":"00:36.040 ","End":"00:41.780","Text":"They didn\u0027t do anything snazzy like try to make the sample balanced"},{"Start":"00:41.780 ","End":"00:46.910","Text":"in terms of gender or maybe geographical origin, anything like that."},{"Start":"00:46.910 ","End":"00:49.460","Text":"They just chose 25 students at random from"},{"Start":"00:49.460 ","End":"00:53.138","Text":"the cohort and that is called a simple random sample."},{"Start":"00:53.138 ","End":"00:55.920","Text":"That\u0027s it. We\u0027re done."}],"Thumbnail":null,"ID":13583},{"Watched":false,"Name":"Exercise 2","Duration":"43s","ChapterTopicVideoID":13103,"CourseChapterTopicPlaylistID":64528,"HasSubtitles":true,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:04.320","Text":"A toy company chooses 5 toys at random from"},{"Start":"00:04.320 ","End":"00:08.355","Text":"each of their 10 models to test for quality control."},{"Start":"00:08.355 ","End":"00:11.620","Text":"What sampling technique was used?"},{"Start":"00:11.620 ","End":"00:21.945","Text":"The clue in this question is the way they say from each of their 10 models."},{"Start":"00:21.945 ","End":"00:24.690","Text":"They\u0027ve got 10 different kinds of toys,"},{"Start":"00:24.690 ","End":"00:26.070","Text":"10 different kinds of models,"},{"Start":"00:26.070 ","End":"00:30.874","Text":"and they sample 5 toys at random from each of the 10 models."},{"Start":"00:30.874 ","End":"00:35.555","Text":"This is called a stratified random sample."},{"Start":"00:35.555 ","End":"00:41.345","Text":"It\u0027s stratified according to each of the 10 models."},{"Start":"00:41.345 ","End":"00:44.400","Text":"That\u0027s it. We\u0027re done."}],"Thumbnail":null,"ID":13584},{"Watched":false,"Name":"Exercise 3","Duration":"1m 35s","ChapterTopicVideoID":13104,"CourseChapterTopicPlaylistID":64528,"HasSubtitles":true,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:04.875","Text":"A researcher is studying opinions about abortion among"},{"Start":"00:04.875 ","End":"00:09.345","Text":"adults aged 25-40 in the Southeastern United States."},{"Start":"00:09.345 ","End":"00:12.915","Text":"She randomly selects 4 states from this region."},{"Start":"00:12.915 ","End":"00:19.280","Text":"Then within those states chooses a simple random sample of adults aged 25-40."},{"Start":"00:19.280 ","End":"00:21.275","Text":"What\u0027s the study\u0027s population?"},{"Start":"00:21.275 ","End":"00:24.005","Text":"What sampling technique was used?"},{"Start":"00:24.005 ","End":"00:28.760","Text":"Well, they tell us that this researcher is studying opinions about abortion"},{"Start":"00:28.760 ","End":"00:34.505","Text":"among all adults aged 25-40 in the Southeastern United States."},{"Start":"00:34.505 ","End":"00:37.325","Text":"That is our studies population."},{"Start":"00:37.325 ","End":"00:42.320","Text":"Now how did this researcher go about creating a random sample?"},{"Start":"00:42.320 ","End":"00:46.760","Text":"The problem tells us that she randomly selected 4 states from this region."},{"Start":"00:46.760 ","End":"00:49.040","Text":"We don\u0027t know exactly how big this region is,"},{"Start":"00:49.040 ","End":"00:50.180","Text":"but I don\u0027t know."},{"Start":"00:50.180 ","End":"00:52.550","Text":"Let\u0027s suppose there is like 8 or 9 states."},{"Start":"00:52.550 ","End":"00:54.905","Text":"She randomly selects 4 of them."},{"Start":"00:54.905 ","End":"00:57.020","Text":"Then within those states,"},{"Start":"00:57.020 ","End":"00:59.425","Text":"she chooses a simple random sample."},{"Start":"00:59.425 ","End":"01:05.130","Text":"This is called a clustered random sample."},{"Start":"01:05.260 ","End":"01:12.980","Text":"It\u0027s a clustered random sample because of this initial stage of randomly"},{"Start":"01:12.980 ","End":"01:15.845","Text":"selecting 4 states from the region and"},{"Start":"01:15.845 ","End":"01:20.450","Text":"then from within those states choosing a sample random sample."},{"Start":"01:20.450 ","End":"01:23.610","Text":"This is called a clustered random sample."},{"Start":"01:23.610 ","End":"01:27.500","Text":"Another word for a cluster is like a group and in this case,"},{"Start":"01:27.500 ","End":"01:32.810","Text":"we\u0027ve got this group of 4 states that are being chosen from the region."},{"Start":"01:32.810 ","End":"01:35.790","Text":"That\u0027s it. We\u0027re done."}],"Thumbnail":null,"ID":13585},{"Watched":false,"Name":"Exercise 4","Duration":"49s","ChapterTopicVideoID":13105,"CourseChapterTopicPlaylistID":64528,"HasSubtitles":true,"VideoComments":[],"Subtitles":[{"Start":"00:00.290 ","End":"00:06.570","Text":"A candidate for Congress polls his friends about their opinions about gun control."},{"Start":"00:06.570 ","End":"00:09.645","Text":"What sampling technique was used?"},{"Start":"00:09.645 ","End":"00:13.560","Text":"In this question, they don\u0027t use the word random at"},{"Start":"00:13.560 ","End":"00:17.745","Text":"all and that\u0027s a clue to you that this is not a random sample."},{"Start":"00:17.745 ","End":"00:24.192","Text":"In fact, another clue is that they say that he polled his friends."},{"Start":"00:24.192 ","End":"00:28.260","Text":"So this is called a convenience sample."},{"Start":"00:28.260 ","End":"00:30.895","Text":"Why is it a convenient sample?"},{"Start":"00:30.895 ","End":"00:35.180","Text":"It\u0027s a convenient sample because the people chosen for the sample were"},{"Start":"00:35.180 ","End":"00:39.516","Text":"the people who were easy or convenient to gather."},{"Start":"00:39.516 ","End":"00:44.760","Text":"This is a convenience sample and this is not random."},{"Start":"00:46.310 ","End":"00:49.690","Text":"That\u0027s it. We\u0027re done."}],"Thumbnail":null,"ID":13586}],"ID":64528},{"Name":"Statistics and Parameters","TopicPlaylistFirstVideoID":0,"Duration":null,"Videos":[{"Watched":false,"Name":"Statistics and Parameters","Duration":"1m 21s","ChapterTopicVideoID":13109,"CourseChapterTopicPlaylistID":64529,"HasSubtitles":true,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:02.460","Text":"In this video, we\u0027ll talk about"},{"Start":"00:02.460 ","End":"00:05.745","Text":"statistics and parameters and the difference between them."},{"Start":"00:05.745 ","End":"00:10.815","Text":"Parameters are measures that always refer to the population."},{"Start":"00:10.815 ","End":"00:13.470","Text":"Statistics on the other hand,"},{"Start":"00:13.470 ","End":"00:19.570","Text":"are numbers or measures that always refer to the sample."},{"Start":"00:20.390 ","End":"00:27.440","Text":"We can take different kinds of measures of the sample or of the population."},{"Start":"00:27.440 ","End":"00:31.994","Text":"For instance, if we find the average and we\u0027re talking about the sample,"},{"Start":"00:31.994 ","End":"00:36.045","Text":"the symbol we use for that is X with a bar on top,"},{"Start":"00:36.045 ","End":"00:37.770","Text":"and we say that X bar."},{"Start":"00:37.770 ","End":"00:43.100","Text":"If we know or given the average for the population,"},{"Start":"00:43.100 ","End":"00:48.080","Text":"which is a parameter that\u0027s indicated with the Greek letter Mu."},{"Start":"00:48.080 ","End":"00:52.865","Text":"If we are measuring the standard deviation of the sample,"},{"Start":"00:52.865 ","End":"00:58.040","Text":"that is given by the lowercase letter s. If we are measuring"},{"Start":"00:58.040 ","End":"01:03.495","Text":"the standard deviation of the population we use a Greek lowercase sigma."},{"Start":"01:03.495 ","End":"01:07.700","Text":"For proportions, if we\u0027ve got a statistic in other words,"},{"Start":"01:07.700 ","End":"01:09.380","Text":"if it\u0027s a proportion of the sample,"},{"Start":"01:09.380 ","End":"01:11.630","Text":"we use P with a little hat on top,"},{"Start":"01:11.630 ","End":"01:13.690","Text":"and that\u0027s called P-hat."},{"Start":"01:13.690 ","End":"01:18.110","Text":"If we are talking about the proportion of the population,"},{"Start":"01:18.110 ","End":"01:19.160","Text":"which is a parameter,"},{"Start":"01:19.160 ","End":"01:21.870","Text":"we just use a lowercase p."}],"Thumbnail":null,"ID":13587},{"Watched":false,"Name":"Example","Duration":"1m 46s","ChapterTopicVideoID":13108,"CourseChapterTopicPlaylistID":64529,"HasSubtitles":true,"VideoComments":[],"Subtitles":[{"Start":"00:00.170 ","End":"00:02.550","Text":"Here\u0027s an example."},{"Start":"00:02.550 ","End":"00:08.700","Text":"25 percent of a state\u0027s voters are thought to support legalization of medical marijuana."},{"Start":"00:08.700 ","End":"00:13.920","Text":"200 voters are randomly sampled and asked whether they support this initiative,"},{"Start":"00:13.920 ","End":"00:18.220","Text":"and 56 indicate their support for the bill."},{"Start":"00:18.470 ","End":"00:21.765","Text":"Part a, what is the population?"},{"Start":"00:21.765 ","End":"00:24.615","Text":"Part b, what is the variable?"},{"Start":"00:24.615 ","End":"00:31.980","Text":"The population are all of the state\u0027s voters. Let\u0027s see."},{"Start":"00:31.980 ","End":"00:42.285","Text":"The variable is the percentage of support for the bill among the state\u0027s voters."},{"Start":"00:42.285 ","End":"00:47.420","Text":"Part c, what parameter is mentioned here? Let\u0027s see."},{"Start":"00:47.420 ","End":"00:49.955","Text":"They told us that 25 percent of"},{"Start":"00:49.955 ","End":"00:54.290","Text":"all the state\u0027s voters are thought to support legalization of medical marijuana."},{"Start":"00:54.290 ","End":"00:55.970","Text":"That\u0027s the parameter."},{"Start":"00:55.970 ","End":"00:57.845","Text":"What kind of parameter is it?"},{"Start":"00:57.845 ","End":"00:59.255","Text":"It\u0027s a proportion."},{"Start":"00:59.255 ","End":"01:01.250","Text":"It\u0027s a population proportion,"},{"Start":"01:01.250 ","End":"01:06.905","Text":"which we denote with the letter P. P is 25 percent or 0.25."},{"Start":"01:06.905 ","End":"01:09.605","Text":"What statistic is mentioned here?"},{"Start":"01:09.605 ","End":"01:12.230","Text":"The statistic refers to the sample,"},{"Start":"01:12.230 ","End":"01:15.545","Text":"the sample of 200 voters. Let\u0027s see."},{"Start":"01:15.545 ","End":"01:19.190","Text":"56 of them indicated their support for the bill."},{"Start":"01:19.190 ","End":"01:22.145","Text":"That is a sample proportion,"},{"Start":"01:22.145 ","End":"01:25.865","Text":"which we denote with a P and a little hat on top of it."},{"Start":"01:25.865 ","End":"01:32.065","Text":"Our P-hat is the 56 out of 200."},{"Start":"01:32.065 ","End":"01:36.200","Text":"If we want to be consistent and express that also as a decimal,"},{"Start":"01:36.200 ","End":"01:38.480","Text":"that\u0027s going to be 0.28,"},{"Start":"01:38.480 ","End":"01:42.470","Text":"and this is our sample proportion,"},{"Start":"01:42.470 ","End":"01:44.510","Text":"which is a statistic."},{"Start":"01:44.510 ","End":"01:47.700","Text":"That\u0027s it. We\u0027re done."}],"Thumbnail":null,"ID":13588},{"Watched":false,"Name":"Exercise 1","Duration":"1m 42s","ChapterTopicVideoID":13110,"CourseChapterTopicPlaylistID":64529,"HasSubtitles":true,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:03.490","Text":"This is the probability distribution of the number of"},{"Start":"00:03.490 ","End":"00:07.450","Text":"flat screen TVs owned by all families in Alphaville."},{"Start":"00:07.450 ","End":"00:11.140","Text":"We sample 4 families from this population and then"},{"Start":"00:11.140 ","End":"00:15.160","Text":"find that these families have on average 2 flat screen TVs."},{"Start":"00:15.160 ","End":"00:19.405","Text":"Give an example of a parameter and of a statistic shown here."},{"Start":"00:19.405 ","End":"00:23.185","Text":"Again, your clue here is this word \u0027all\u0027,"},{"Start":"00:23.185 ","End":"00:28.405","Text":"the word \u0027all\u0027 tells us that the chart refers to the entire population."},{"Start":"00:28.405 ","End":"00:32.680","Text":"We can construct a parameter since we\u0027ve got"},{"Start":"00:32.680 ","End":"00:38.865","Text":"the whole population and find the average number of flat screen TVs per family."},{"Start":"00:38.865 ","End":"00:44.510","Text":"To do that, we would take each category of flat screen TVs and"},{"Start":"00:44.510 ","End":"00:50.150","Text":"multiply it by the number of families in that category and so we\u0027ve got 50 times 0,"},{"Start":"00:50.150 ","End":"00:52.010","Text":"250 times 1,"},{"Start":"00:52.010 ","End":"00:54.625","Text":"350 times 2,"},{"Start":"00:54.625 ","End":"01:00.735","Text":"300 times 3, and 50 times 4."},{"Start":"01:00.735 ","End":"01:04.940","Text":"Altogether, if you add up the number of families here,"},{"Start":"01:04.940 ","End":"01:07.460","Text":"we\u0027ve got 1,000 families."},{"Start":"01:07.460 ","End":"01:11.600","Text":"If you do that multiplication and addition,"},{"Start":"01:11.600 ","End":"01:16.380","Text":"you\u0027ll get 2,050 and that numerator."},{"Start":"01:16.380 ","End":"01:22.190","Text":"Our average for the population is 2.05."},{"Start":"01:22.190 ","End":"01:25.115","Text":"We have a Mu of 2.05."},{"Start":"01:25.115 ","End":"01:30.500","Text":"The problem also wants to know an example of a statistic and it tells us that"},{"Start":"01:30.500 ","End":"01:35.600","Text":"there\u0027s a sample of 4 families and that they have on average 2 flat screen TVs each."},{"Start":"01:35.600 ","End":"01:38.180","Text":"That\u0027s an example of an x-bar."},{"Start":"01:38.180 ","End":"01:41.500","Text":"x-bar is 2."}],"Thumbnail":null,"ID":13589},{"Watched":false,"Name":"Exercise 2","Duration":"1m 7s","ChapterTopicVideoID":13111,"CourseChapterTopicPlaylistID":64529,"HasSubtitles":true,"VideoComments":[],"Subtitles":[{"Start":"00:00.650 ","End":"00:05.940","Text":"Assume that 20 percent of a large company\u0027s employees have graduate degrees."},{"Start":"00:05.940 ","End":"00:08.780","Text":"10 employees are randomly selected from the company,"},{"Start":"00:08.780 ","End":"00:10.905","Text":"and 3 of them have graduate degrees."},{"Start":"00:10.905 ","End":"00:13.020","Text":"Part A, what is the population?"},{"Start":"00:13.020 ","End":"00:18.790","Text":"Our population here is the large company\u0027s employees."},{"Start":"00:24.050 ","End":"00:27.045","Text":"Part B, what is the variable?"},{"Start":"00:27.045 ","End":"00:33.040","Text":"Our variable here is the proportion of employees with graduate degrees."},{"Start":"00:38.510 ","End":"00:41.955","Text":"Part C, what\u0027s the parameter?"},{"Start":"00:41.955 ","End":"00:47.990","Text":"Our parameter here is that 20 percent of the company\u0027s employees have graduate degrees."},{"Start":"00:47.990 ","End":"00:50.720","Text":"So that is our value for p, lowercase p,"},{"Start":"00:50.720 ","End":"00:54.605","Text":"because it\u0027s the proportion for the population."},{"Start":"00:54.605 ","End":"01:01.907","Text":"Our statistic is 3/10 or 30 percent"},{"Start":"01:01.907 ","End":"01:06.450","Text":"and that we denote with a p hat."}],"Thumbnail":null,"ID":13590},{"Watched":false,"Name":"Exercise 3","Duration":"1m 33s","ChapterTopicVideoID":13112,"CourseChapterTopicPlaylistID":64529,"HasSubtitles":true,"VideoComments":[],"Subtitles":[{"Start":"00:00.050 ","End":"00:06.315","Text":"10 students are sampled from all students at a college who completed statistics 101."},{"Start":"00:06.315 ","End":"00:09.405","Text":"The average course grade for all students is 78,"},{"Start":"00:09.405 ","End":"00:11.775","Text":"with a standard deviation of 15."},{"Start":"00:11.775 ","End":"00:15.060","Text":"The average grade among the students in the sample is 80,"},{"Start":"00:15.060 ","End":"00:17.295","Text":"with a standard deviation of 18."},{"Start":"00:17.295 ","End":"00:19.785","Text":"Part a, what is the population?"},{"Start":"00:19.785 ","End":"00:30.100","Text":"The population here is all students who completed Stats 101."},{"Start":"00:32.690 ","End":"00:35.945","Text":"Part b, what is the variable?"},{"Start":"00:35.945 ","End":"00:40.915","Text":"The problem was talking about course grades so variable is the course grade."},{"Start":"00:40.915 ","End":"00:44.780","Text":"Part c, what parameters are included here?"},{"Start":"00:44.780 ","End":"00:48.515","Text":"Your clue for that is the word all,"},{"Start":"00:48.515 ","End":"00:55.460","Text":"the all students refers to the population and the average for the population is 78."},{"Start":"00:55.460 ","End":"01:01.670","Text":"We denote the average for the population with the letter Mu and it is 78."},{"Start":"01:01.670 ","End":"01:07.385","Text":"We denote the standard deviation for the population with the letter Sigma and it is 15."},{"Start":"01:07.385 ","End":"01:09.530","Text":"Part d, what is the sample size?"},{"Start":"01:09.530 ","End":"01:13.010","Text":"Well, they tell us that there are 10 students being sampled,"},{"Start":"01:13.010 ","End":"01:14.905","Text":"so n is 10."},{"Start":"01:14.905 ","End":"01:17.915","Text":"In Part e, what statistics will be used here?"},{"Start":"01:17.915 ","End":"01:19.340","Text":"They tell us in the problem that"},{"Start":"01:19.340 ","End":"01:22.520","Text":"the average grade among the students in the sample is 80,"},{"Start":"01:22.520 ","End":"01:26.175","Text":"so that\u0027s an X bar so it\u0027s the sample mean."},{"Start":"01:26.175 ","End":"01:30.170","Text":"They tell us that the standard deviation of the sample is 18,"},{"Start":"01:30.170 ","End":"01:33.450","Text":"and we mark that with a lowercase s."}],"Thumbnail":null,"ID":13591}],"ID":64529}]

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