00:05
A department store is sending a survey, or mailing a survey, to people who make credit card purchases at their store.
00:17
Forty -five thousand people made credit card purchases at their store.
00:24
The store sends or mails surveys to 1 ,000 of those people.
00:32
Out of the 1 ,000 people that received a survey in the mail, only 137 of them returned the survey.
00:45
First of all, this is an example of a voluntary response sample.
00:53
Surveys were mailed to 1 ,000 people.
00:58
Only 137 of those thousand voluntarily responded to the survey.
01:08
And these are typically very biased samples.
01:13
All right.
01:14
So we need to know who is the population, identify the population, and identify the sample.
01:22
The population are all the people who made credit card purchases at the store.
01:42
We're trying to find out something or make some kind of draw some conclusions about all the people that make credit card purchases at the store...