Question 1

Which of the following best describes an observational study?

Accepted Answer

Researchers observe or measure characteristics of subjects without attempting to influence or modify them.

Question 2

A study is conducted to determine whether a new herbal remedy reduces the severity of colds. Participants are randomly assigned to receive either the remedy or a placebo. Which type of study is this?

Accepted Answer

Experiment

Question 3

In an experiment, what is the main purpose of the control group?

Accepted Answer

To serve as a baseline for comparison by not receiving the treatment

Question 4

Which of the following is an example of a prospective study?

Accepted Answer

Researchers follow a group of smokers and non-smokers over ten years to observe the development of lung cancer.

Question 5

A variable that may explain or cause the effect in a statistical study is called:

Accepted Answer

Explanatory variable

Question 6

In a study of the effects of magnets on back pain, some subjects were treated with magnets while others received non-magnetic devices that looked similar. What is the purpose of the non-magnetic devices?

Accepted Answer

To act as a placebo, preventing subjects from knowing whether they are receiving the real treatment

Question 7

Which of the following best describes confounding in an experiment?

Accepted Answer

The effects of different variables are mixed, making it impossible to determine the individual effects of the variables of interest.

Question 8

A study divides college students into two groups. One group listens to classical music before a task, the other does not. The group that listened to music performed better immediately after listening. In this experiment, what is the treatment?

Accepted Answer

Listening to classical music before the task

Question 9

Which strategy is most effective in avoiding confounding when assigning subjects to treatment and control groups?

Accepted Answer

Assigning subjects at random and using sufficiently large groups

Question 10

What is the placebo effect?

Accepted Answer

When patients improve simply because they believe they are receiving a useful treatment

Question 11

In a double-blind experiment, who knows which subjects are in the treatment or control group?

Accepted Answer

Neither the subjects nor the experimenters

Question 12

A meta-analysis is best described as:

Accepted Answer

A review of many individual studies considered as a combined group to find trends

Question 13

A researcher wants to know whether teens who try marijuana are more likely to abuse hard drugs as adults. Which type of study should be conducted?

Accepted Answer

Prospective observational study

Question 14

Which of the following is a common problem in experiments that can be avoided by blinding?

Accepted Answer

Placebo effect and experimenter effect

Question 15

In a study, fifty coffee-drinkers are told not to drink coffee before an exam, and fifty non-coffee-drinkers are asked to drink coffee before the exam. Both groups perform equally. What is the main flaw in this experiment?

Accepted Answer

The groups were not randomly assigned, so pre-existing differences may confound the results.

Question 16

A chiropractor performs adjustments on 25 patients with back pain. Afterward, 18 say they feel better. He concludes the adjustments are effective. What is the main issue with this conclusion?

Accepted Answer

There is no control group, so improvement could be due to placebo effect or other factors.

Question 17

Which equation best represents the probability of randomly assigning a subject to either the treatment or control group in a fair experiment?

Accepted Answer

$$P = \frac{1}{2}$$

Question 18

In a single-blind experiment, who is unaware of which group the subjects belong to?

Accepted Answer

The subjects

Question 19

Which of the following best describes a response variable?

Accepted Answer

A variable that responds to changes in the explanatory variable

Question 20

A study identifies six people with a rare disease and randomly assigns three to exercise daily and three to avoid exercise. After six months, degeneration is compared. What is the main flaw?

Accepted Answer

The sample size is too small to avoid confounding and ensure reliable results.

Types of Statistical Studies: Observational Studies, Experiments, and Study Design

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