4.1 Why Take Samples, and How Not To

4.1 Why Take Samples, and How Not To

Reading Guide

Taking a sample survey can help you ______. ______is a primary reason to use samples. Whenever testing destroys the things you test, your only choice is to ______.

There’s a tradeoff between the ______and the amount and quality ______.

Using a sample allows you to ______.

Census vs. Sample

In statistics, the set of people of things that you want to know about is called ______. The individual elements of the populations sometimes are called ______.

Definition of population in everyday language: / Definition of population in statistics:

The number of units is called the ______.

The ______is the set of units you do get to study. The special case where you collect data on the entire population is a ______.

Who is Nielsen Media Research?

Parameter:

Statistic:

Bias: A Potential Problem with Survey Data

Two ways to get untrustworthy results from a sample

Definition of bias in everyday language: / Definition of bias in statistics:

Sampling bias lies in the ______not in the ______.

What makes a good sample?

How can I tell if my sample is representative?

Sample Selection Bias

______or ______, is present in a sampling method if samples tend to result in estimates of ______.

Size bias is ______.

Example of size bias:

Voluntary response bias is ______.

Example of voluntary response bias:

Convenience sampling is ______.

Example of convenience sample:

Judgment samples are ______.

Example of a judgment sample:

An unbiased sampling method requires that ______. So you must prepare ______, called the sampling frame.

If you start with a bad frame, ______.

Bad frame, ______.

Response Bias

Bias doesn’t always come from the ______. Bias from other sources can contaminate data ______.

Perhaps the worst case of faulty data is ______.

Nonresponse bias can occur when ______.

Example of nonresponse bias:

Questionnaire bias arises from ______.

Example of questionnaire bias:

Another problem polls and surveys have is trying to ensure that ______.

Bias from incorrect responses might be the result of ______, but it is more likely to come from ______, including ______.