Experimental Design

Researchers were interested to know whether internal vehicle temperatures vary by outside temperatures. To evaluate this, temperature rise was measured continuously over a 60-minute period in a dark SUV on 16 different clear, sunny days with outside temperatures ranging from 72^oF to 96^oF. The researchers' method of analysis is best described as:

• a census.

• a survey.

• an observational study.

• a randomized comparative experiment.

• a single-blind randomized comparative experiment.

Runners after an ultramarathon commonly develop respiratory infections. We want to know if taking 600 milligrams of vitamin C daily will reduce these infections. Researchers randomly assigned 100 ultramarathon runners to receive either vitamin C or placebo. All subjects were watched for 14 days after the big race to see if infections developed. The type of design used here?

• matched pairs
• randomized block
• completely randomized
• stratified 

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

• a completely randomized experiment
• an observational study
• a stratified sample
• a matched pairs experiment

True or False: An example of a matched pair experimental design is having one twin receive treatment A and the second twin receive treatment B

• True
• False

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

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.

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 in the picture?

• Randomized Block Design

• Completely Randomized Design

• Matched Pairs

• SRS

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.