Experimental Design AP Statistics

In the previous problem, supposed that the researchers suspected that women over the age of 55 may respond differently to the treatment. Given that a random sample of 40,000 women over the age of 45 has already been chosen, the study would have been improved by:

• a stratified sample, with strata determined by age.

• a stratified sample, with strata determined by gender.

• a block design, with blocks determined by age.

• a block design, with blocks determined by gender.

• a double-blind completely randomized design.

Left-handedness is the preference for the left hand over the right for everyday activities such as writing. Studies indicate that about 93% of the population may be characterized as right-handed. Researchers would like to conduct a study to determine if left-handed teens differ significantly in their ability to memorize facts than right-handed teens. Suppose the researchers concluded that the average number of words memorized by left-handed teens was statistically significantly higher than the average number memorized by right-handed teens. In this context, statistically significant means that:

• the number of words memorized by left-handed students exceeded the number memorized by right-handed students.

• the average number of words memorized by left-handed students exceeded the average number memorized by right-handed students.

• right-handed students tend to not do as well as left-handed students in memorizing words.

• it would be unlikely to observe an average difference as large as was observed by chance variation.

• a randomized, controlled experiment was conducted.

What kind of experiment is shown in the picture?

• Randomized Block Design

• Completely Randomized Design

• Matched Pairs

• SRS

A market research company wishes to find out whether the population of students at a university prefers Starbucks or Dunkin Donuts. A random sample of students is selected, and each student is asked first to try both but the order they try them is randomly decided with a coin toss (heads: Starbucks, then Dunkin. tails: vice versa). They then indicate which brand they prefer. This is an example of

• completely randomized experiment

• observational study

• stratified sample

• matched pairs experiment

Which of the following is a key distinction between well designed experiments and observational studies?

• More subjects are available for experiments than for observational studies.

• Ethical constraints prevent large-scale observational studies.

• Experiments are less costly to conduct than observational studies.

• An experiment can show a direct cause-and-effect relationship, whereas an observational study cannot.

• Tests of significance cannot be used on data collected from an observational study.

Does listening to classical music while studying increase test scores?

• Survey

• Observational study

• Experimental study

What type of study is described? A gym tries out a new weightlifting method to see if it will build muscle for their customers faster than their current method.

• Sample Survey

• Experiment

• Observational Study

To investigate the effectiveness of an herbal medication for pain relief, a researcher randomly selected 80 patients who were undergoing physical therapy while recovering from an injury. Of the patients, 40 had knee injuries, 16 had arm injuries, and 24 had foot injuries. The researcher will use two treatments for the investigation: the herbal medication and a standard medication. After the patients are on the medication for two weeks, the amount of pain reduction will be measured for each patient. Which of the following best describes why a randomized block design is appropriate for the investigation?

• The 80 patients were selected at random from all patients undergoing physical therapy while recovering from an injury.

• The sample size was greater than 30.

• Each patient will be randomly assigned to either the herbal medication or the standard medication.

• Blocking on injury type will help to separate natural variability from differences due to injury type.

• Each patient assigned to the herbal medication will be paired with a patient assigned to the standard medication.

What kind of experiment is shown?

• Matched Pairs

• Block Design

• Completely Randomized Design

• SRS

An experiment will be conducted to determine whether children learn their multiplication facts better by practicing with flash cards or by practicing on a computer. Children who volunteer for the experiment will be randomly assigned to one of the two treatments. Because the children’s gender may affect the outcome, there will be blocking by gender. After practice, the children will be given a test on their multiplication facts. Why will it be impossible to conduct a double-blind experiment?

• The experimenter will know whether the child is a boy or a girl and whether he or she used flash cards or the computer.

• The child will know whether he or she is a boy or a girl.

• The child will know whether he or she used flash cards or the computer.

• The person who grades the tests will know whether the child was a boy or a girl.

• The person who grades the tests will know whether the child used flash cards or the computer.