Deck 2: Collecting Data Sensibly

Question 1

A study is an observational study if the investigator observes the behavior of a response variable when one or more factors are manipulated.

Answer 1

False

Question 2

Random subpopulations of a population are called strata.

Answer 2

False

Question 3

Selection bias can occur if volunteers only are used in a study.

Answer 3

True

Question 4

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

Question 5

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

Question 6

As long as the sample size is small relative to the population, there is little practical difference between sampling with replacement and sampling without replacement.

Question 7

By definition, a simple random sample of size n is any sample that is selected in a manner to guarantee every individual in the population has an equal chance of selection.

Question 8

If the subjects as well as the person measuring the response are aware of the treatment assigned to the subject, only single-blinding is being used.

Question 9

Stratified sampling is a sampling method that in no way involves simple random sampling.

Question 10

Blocking is a technique that can be used to filter out the effects of extraneous factors.

Question 11

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

Question 12

Replicating in an experiment means that the number of subjects is greater than 1.

Question 13

A placebo is identical in appearance to the treatment of interest, but contains no active ingredients.

Question 14

In a well-designed experiment, the factors are confounded whenever possible.

Question 15

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

Question 16

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

Question 17

Response bias can occur when responses are not actually obtained from all individuals selected for inclusion in the sample.

Question 18

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

Question 19

Increasing sample size will generally eliminate bias in a sample.

Question 20

Random assignment of volunteers should result in comparable experimental groups.

Question 21

The ZZZ chain of motels has a standard method of constructing their rooms to maximize the ease of parking for its customers.The rooms are arranged in adjacent buildings so that each customer can park outside the rented room.The layout for one of the with 48 rooms located along a famous highway is diagrammed below:

Question 22

A friend of yours, who is not taking statistics, wonders why it is that anyone would choose to take a sample."Obviously," she says, "you would get better information from a census." In a short paragraph, explain why it is that statisticians take samples rather than taking a census.

Question 23

The most basic sampling method studied in statistics is the simple random sample (SRS).In your own words, what is the correct definition of a simple random sample of size n?

Question 24

The following paragraph describes an actual study.After reading the description, determine whether the study is an observational study or an experiment.Justify your answer with specific references to the information in the study. "We compared paired daytime and night counts of wild brook trout, brown trout, and rainbow trout made by the same snorkelers in five streams during August 1994.Overall, we counted 109 trout in the daytime and 333 trout at night.We speculate that trout counted at night were present during the daytime but were hidden from view.Biologists should consider that trout behavior and susceptibility to being seen might vary a great deal between daytime and night, even during summer.In some streams, the majority of trout may not be seen during the daytime."

Question 25

Three methods for random sampling are: (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.Specifically, what sampling circumstances would lead you to choose each of these methods?

Question 26

The following paragraph describes an actual study.After reading the description, determine whether the study is an observational or experimental study.Justify your answer with specific references to the information in the study. "Before the opening of the new International Airport and the termination of the old airport, children near both sites were recruited into aircraft-noise groups (aircraft noise at present or pending)and control groups with no aircraft noise and closely matched for socio-economic status.A total of 326 children (mean age = 10.4 years)took part in three data-collection waves, one before and two after the switch-over of the airports.After the switch to the new airport, long- term memory and reading were found to be impaired in the noise group at the new airport, and improved in the formerly noise-exposed group at the old airport."

Question 27

In competitive sports, video recorders have been used more frequently in recent years. The idea behind the recorder is that coaches can replay training sessions for more effective feedback to the athlete.Some people believe video recording may make the athletes more nervous and actually decrease their performance.You have been asked to design an experiment to address this issue for competitive high school tennis players. You have decided to use the accuracy of tennis serves as your response variable, and the number of successful serves out of 100 as your performance measure.The subjects for your experiment are 60 high school male competitive tennis players of varying ability who have volunteered for the experiment.

Question 28

The two paragraphs below discuss aspects of two studies, each of which exhibit a bias.For each study, decide whether the problem is selection bias, response bias, or nonresponse bias, and in a few sentences explain why you chose your answer.