Unit 2 Test Review Test on _________________
You need to know:

Ways to Sample

SRS

Stratified Random Sampling

Cluster Sampling

Convenience Sampling

Voluntary Response Sampling

Types of Bias

Undercoverage

Response Bias

Nonresponse Bias

Voluntary Response Bias

Wording Bias

Different Experiment Designs

Comparative Random Design

Block Design

Matched Pairs Design (i)

Matched Pairs Design (ii)

Observational Study vs. Experiment

Different Goals

Hands On/Hands Off

How to design an experiment (well)
Practice:
1. Under which of the following conditions is it preferable to use stratified random sampling rather than simple random sampling?

The population can be divided into a large number of strata so that each stratum contains only a few individuals.

The population can be divided into a smaller number of strata so that each stratum contains a large number of individuals.

The population can be divided into strata so that the individuals in each stratum are as much alike as possible.

The population can be divided into strata so that the individuals in each stratum are as different as possible.

The population can be divided into strata of equal sizes to that each individual in the population still have the same chance of being selected.
2. Which of the following is (are) important in designing an experiment?
I. Control of all variables that might have an influence on the response variable.
II. Randomization of subjects to treatment groups
III. Use of a large number of subjects to control for smallsample variability

I only

I and II only

II and III only

I, II, and III

II only
3. George and Michelle each claimed to have the better recipe for chocolate chip cookies. They decided to conduct a study to determine whose cookies were really better. They each baked a batch of cookies using their own recipe. George asked a random sample of his friends to takes his cookies and to complete a questionnaire on their quality. Michelle asked a random sample of her friends to complete the same questionnaire for her cookies. They then compared the results. Which of the statements about this study is false?

Because George and Michelle have a different population of friends, their sampling procedure makes it difficult to compare the recipes.

Because George and Michelle each used only their own respective recipes, their cooking ability is confounded with the recipe quality.

Because George and Michelle each used only the ovens in their houses, the recipe quality is confounded with the characteristics of the oven.

Because George and Michelle used the same questionnaire, their results will generalize to the combined population of friends.

Because George and Michelle each baked one batch, there is no replication of the cookie recipes.
Free Response:
A local school board plans to conduct a survey of parentsâ€™ opinions about yearround schooling in elementary schools. The school board obtains a list of all families in the district with at least one child in an elementary school and sends the survey to a random sample of 500 of the families. The survey question is provided below.
A proposal has been submitted that would require students in elementary schools to attend school on a yearround basis. Do you support this proposal? (Yes or No)
The school board received responses from 98 of the families, with 76 of the responses indicating support for yearround schools. Based on this outcome, the local school board concludes that most of the families with at least one child in elementary school prefer yearround schooling.

What is a possible consequence of nonresponse bias for interpreting the results of this survey?

Someone advised the local school board to take an additional random sample of 500 families and use the combined results to make their decision. Would this be a suitable solution to the issue raised in part (a)? Explain.

Suggest a different followup step from the one suggested in part (b) that the local school board could take to address the issue raised in part (a).
