Exam 6: Experiments in the Real World

Volunteers for a human performance study were randomly divided into two groups. The first group had their flexibility measured in the morning after a short meditation session while the second group had their flexibility measured in the afternoon with no previous meditation session. The flexibility scores of the two groups were compared. This experiment was not double-blind because:

A scientist is designing a clinical trial to test the effect of online chat counseling with migraine sufferers as a supplementary treatment in combating their migraines. Migraine sufferers will have access to counselors via online chat software; the scientist plans to see whether their migraine pain has been reduced after six weeks. If the trial doesn't include a control group, the data will be invalid because of:

In comparative drug studies, double-blind experiments are typically used. The purpose of keeping the diagnosing physicians ignorant of the treatment status of the experimental subjects is to

The keys to convincing experiments are

A professor believes that students who smoke cigarettes tend to have lower grades. He collects data from 1326 randomly selected students at his university and discovers that, on average, students who smoke cigarettes do indeed tend to have lower grade point averages than students who do not smoke. Does this study give strong evidence that smoking cigarettes causes lower grades?

Volunteers for a human performance study were randomly divided into two groups. The first group had their flexibility measured in the morning after a short meditation session while the second group had their flexibility measured in the afternoon with no previous meditation session. The flexibility scores of the two groups were compared. The study design for this experiment is called a(n):

In a randomized block design the blocks often represent levels of

To see if eating just before going to bed causes nightmares, volunteers are recruited to spend the night in a sleep laboratory while connected to machines that monitor their sleep patterns. They are randomly assigned to be given a meal before bed or not. Numbers of nightmares are recorded and compared for the two groups. The critics claim the study

A farmer wishes to determine which of two brands of baby-pig pellets, Kent or Moormans, produces better weight gain. Two of his sows each give birth to litters of 10 pigs on the same day, so he decides to give the baby pigs in litter A only Kent pellets, while the pigs in litter B will get only Moormans pellets. After four weeks, the average weight gain for pigs in litter A is greater than the average weight gain for pigs in litter B. The feed they get is not the only factor affecting the rate at which pigs gain weight. Genetic differences also affect weight gain. It is likely that the pigs in litter A are genetically different from the pigs in litter B since the two litters have different mothers. What experimental design technique could the farmer use to take into account the genetic differences?

We say that the design of a study is biased if which of the following is true?

A professor believes that students who smoke cigarettes tend to have lower grades. He collects data from 1326 randomly selected students at his university and discovers that, on average, students who smoke cigarettes do indeed tend to have lower grade point averages than students who do not smoke. This study was based on

The difference between an experiment and an observational study is that