AP Statistics Review Unit III

Can pleasant aromas help a student learn better? Two researchers believed that the presence of a floral scent could improve a person's learning ability in certain situations. They had 22 people work through a pencil-and-paper maze 6 times. Three of the times they wore a floral-scented mask and three times they wore an unscented mask. The three trials for each mask followed one another. Testers measures the length of time it took subjects to complete each of the six trials. They reported that, on average, subjects wearing the floral-scented mask completed the maze more quickly that those wearing the unscented mask, although, the difference was not statistically significant. This study is:

• a convenience sample
• an oberservational study
• an experiment, but not double-blind
• a double-blind experiment

A study of human development showed two types of movies to groups of children. Crackers were available in a bowl, and the investigators compared the number of crackers eaten by children watching the different kinds of movies. One kind of movie was shown at 8 AM (right after the children had breakfast) and another at 11 AM (right before the children had lunch). It was found that during the movie shown at 11 AM, more crackers were eaten than during the movie shown at 8 AM. The investigators concluded that the different types of movies had an effect on appetite.
The results cannot be trusted because

• the study was not double-blind. Neither the investigators nor the children should have been aware of which movie was being shown.
• the investigators were biased. They knew beforehand what they hoped the study would show.
• the investigators should have used several bowls, with crackers randomly placed in each.
• the time the movie was shown is a confounding variable.

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CCSS.HSS.IC.B.3

Consider an experiment to investigate the effectiveness of different insecticides in controlling pests and their effects on subsequent yield. What is the best reason for randomly assigning treatment levels (spraying or not spraying) to the experimental units (farms)?

• Randomization makes the experiment easier to conduct since we can apply the insecticide in any pattern rather than in a systematic fashion.
• Randomization will tend to average out all other uncontrolled factors such as soil fertility so that they are not confounded with the treatment effects.
• Randomization makes the analysis easier since the data can be collected and entered into the computer in any order.
• Randomization is required by statistical consultants before they will help you analyze the experiment.

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CCSS.HSS.IC.B.3

CCSS.HSS.IC.B.5

The most important advantage of experiments over observational studies is that

• A) experiments are usually easier to carry out
• B)Experiments can usually give better evidence of causation
• C) Confounding cannot happen in experiments
• D) Observational studies cannot use random samples

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CCSS.HSS.IC.B.3

CCSS.HSS.ID.C.9

In order to perform an experiment using 60 members of a gym, I first divide the list of members into men and women because I feel that the results will be different based on gender. I then randomly choose 30 men and 30 women. I assign half of the men to the treatment group and half to the control group. I repeat this procedure with the women. This is an example of a:

• randomized comparative design
• blocking design
• matched pairs design
• double blind simple random sample

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CCSS.HSS.IC.B.3

CCSS.HSS.IC.B.5

A recent study showed that tea drinkers have lower stress levels than coffee drinkers. Tea drinkers are known to have a higher proportion of yoga practitioners than coffee drinkers, and they exercise on average two hours per week more than their coffee-drinking counterparts. What is the term used to describe these additional factors that might have an effect on the stress levels of tea drinkers?

• cause and effect variables
• confounding variables
• sampling variables
• unfounded variables

Principal Rusk picks 75 students at a recent varsity football game to be used for the sample.  This is what type of sampling design?

• SRS
• Stratified
• Convenience
• Voluntary Response

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CCSS.HSS.IC.B.3

Each student in the school is assigned a different number.  75 unique numbers are selected for the sample using a RDT.  This is what type of sampling design?

• Stratified
• SRS
• Cluster
• Convenience

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CCSS.HSS.IC.B.3

Each student in the school is given a different number.  A student is randomly selected from the first 25. That student and every 25^th student thereafter are in the sample.  This is what type of sampling design?

• SRS
• Systematic
• Multistage
• Stratitfied

An SRS of 25 students is taken from each grade to form the sample.  This is what type of sampling design?

• Cluster
• SRS
• Stratified
• Multistage

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CCSS.HSS.IC.B.3

CCSS.HSS.IC.A.1