Overall Notes

• There is one version of this assessment provided in the Teacher Resources Materials (TRM). Use this assessment as-is or use it as a model to create your own. 

• If you are making your own assessment, consider using the test bank and the ExamView software.

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Common Student Errors

• Students often have trouble distinguishing between an observational study and an experiment. Remind them that for an experiment a treatment is imposed, while an observational study does not attempt to influence responses. 

• Students often confuse nonresponse and voluntary response bias. Voluntary response is an open invite to people to join a study. For nonresponse, the person has already been chosen to be part of the study, they just decide not to participate. 

• The common English meaning of bias (having a strong opinion) is not the same as the statistical meaning of bias (consistently missing the mark when estimating a parameter). 

• In the Beyonce activity, a convenience sample yielded estimates that were biased, as they consistently overestimated the truth. A sampling method that consistently underestimates the truth also shows bias. 

• When students are describing a method to take a random sample using slips of paper, they often forget to mention “equal sized slips” and “shuffle the slips”. 

• When students are describing a method to take a random sample using technology, they often forget to mention “ignore repeats”. 

• Students often claim that increasing the sample size increases the accuracy of the estimates. The increase in sample size does not change the accuracy, but it does make the estimates more precise (less variable).