Exam 1: Collecting Data in Reasonable Ways

The ZZZ chain of motels has a standard method of constructing their buildings to maximize the ease of parking for its customers. The rooms are arranged in adjacent buildings, A and B, so that customers can park close to their rooms. The layout for the 48-room motels is diagrammed below: Route 66 Building A Building B The manager wishes to assess customer satisfaction with the motel services. His plan is to survey the adults in each of 12 rooms. The cleaning staff will place surveys on the customers' beds before they check in to the motel. In order to make the directions easy for the cleaning staff to follow, he elects to use systematic sampling. a) Describe carefully how you would use random numbers to set up the systematic sampling process. (In your description you may assume you have a random number table, but do NOT carry out the procedure you describe.) b) Write a short paragraph for the cleaning staff that explains how to carry out your method in part (a). The members of the cleaning staff have not taken statistics, so the use of statistical terminology will not be helpful.

Bias is the tendency for samples to differ from the corresponding population in some systematic way. Some types of bias are: (a) selection bias, (b) response bias, and/or (c) nonresponse bias. In a few sentences, discuss the differences among these different types of bias. Examples may illustrate, but not substitute for, a discussion.

Consider the following three methods for random sampling: (a) simple random sampling, (b) stratified random sampling, and (c) cluster sampling. In a few sentences, discuss the similarities and differences among these sampling methods. What aspects of the population would lead you to choose each of these methods? The paragraphs below in questions 2 and 3 present information about a health study. Each gives a hint about possible bias. Decide whether the possible bias is (i) selection bias, (ii) response bias, or (iii) nonresponse bias, and explain why you chose your answer.

Increasing sample size will eliminate bias in a sample.

Clusters are non-overlapping subgroups of a population that have been identified as homogeneous.

Variables are extraneous if their effects on the response variable cannot be distinguished from one another.

Blocking is used to filter out the effects of some extraneous variables.

A control group provides a baseline for comparison with a treatment group.

After reading the description below, determine whether the study is an observational or experimental study. Justify your answer with specific references to the information in the study. "Before expanding the regional airport, children living nearby were determined to be in one of two aircraft-noise groups (i) aircraft noise at present or (ii) aircraft noise would come with the expansion. Three hundred twenty-six children (mean age = 10.4 years) took part in three data-collection waves, one before and two after the expansion of the airports. After the expansion, long- term memory and reading were found to be impaired in the group newly exposed to aircraft noise."

The ZZZ chain of motels has a standard method of constructing their buildings to maximize the ease of parking for its customers. The rooms are arranged in adjacent buildings, A and B, so that customers can park close to their rooms. The layout for the 48-room motels is diagrammed below: Route 66 Building A Building B The manager wishes to assess customer satisfaction with the motel services. His plan is to survey the adults in each of 12 rooms. The cleaning staff will place surveys on the customers' beds before they check in to the motel. As she tries to decide on an appropriate sampling strategy, the manager realizes the rooms in Building A might be noisier than Building B, and this should be taken into account. a) What sampling strategy should she use in this situation? Provide appropriate statistical justification. b) Write a short paragraph for the cleaning staff that explains how to carry out your method in part (a). The members of the cleaning staff have not taken statistics.

We have distinguished two types of studies: observational and experimental. Briefly explain the difference between these two types of study. You may use an example to support your answer but not as a substitute for an explanation.

Explain how you would determine if a variable is an explanatory variable or an extraneous variable? Again, you may use an example to support your answer but not as a substitute for an explanation.

In a well-designed experiment the treatments are confounded with other variables whenever possible.

Stratified sampling does not involve simple random sampling.

Selection bias occurs if only volunteers are used in a study.

A treatment is a particular combination of values for the explanatory variables.

Bias is a potentially serious problem that can arise in surveys. a) In a few sentences, explain the concept of bias. b) What is the distinction between selection bias and non-response bias?

The method of control wherein an extraneous variable is held constant is called blocking.

Random assignment to treatments will guarantee that treatment groups are exactly alike for experimental purposes.

Bias is a potentially serious problem that can arise in surveys. a) In a few sentences, explain the concept of bias. b) What is the distinction between response bias and non-response bias?