Question 1

Which of the following best describes the difference between an observational study and a designed experiment?

Accepted Answer

In an observational study, researchers observe subjects without influencing variables, while in a designed experiment, researchers assign treatments and intentionally change explanatory variables.

Question 2

In the study where researchers followed 791,710 women in the UK to investigate the association between mobile phone use and brain tumors, what type of study was conducted?

Accepted Answer

Observational study

Question 3

In the rat study investigating radio-frequency radiation (RFR) and brain tumors, which variable did the researchers intentionally manipulate?

Accepted Answer

The type and amount of radio-frequency radiation exposure

Question 4

Which of the following is a lurking variable in the study examining the association between TVs in the bedroom and adolescent obesity?

Accepted Answer

Socioeconomic status

Question 5

In the influenza vaccine study on seniors, which variable is the response variable?

Accepted Answer

Hospitalization or death from pneumonia or influenza

Question 6

Why did the authors of the influenza vaccine study use the term 'associated' instead of 'caused' when describing the relationship between flu shots and lower risk of hospitalization or death?

Accepted Answer

Because the study was observational and confounding variables may exist

Question 7

A study randomly divides seventh grade students into two groups, teaching one group with traditional methods and the other with reform methods, then compares achievement test scores after one year. What type of study is this?

Accepted Answer

Designed experiment

Question 8

In the study about TVs in the bedroom and adolescent BMI, what is the explanatory variable?

Accepted Answer

Presence of a TV in the bedroom

Question 9

Which statement about confounding variables is correct?

Accepted Answer

Confounding occurs when the effects of two or more explanatory variables are not separated, making it unclear which variable is responsible for changes in the response variable.

Question 10

A researcher observes that countries with more televisions per household have higher life expectancy. Which of the following best explains why buying more TVs may not cause people to live longer?

Accepted Answer

There may be lurking variables, such as wealth or access to healthcare, that influence both TV ownership and life expectancy.

Question 11

In the influenza vaccine study, which of the following could be a confounding variable?

Accepted Answer

Age, health status, or mobility of the seniors

Question 12

Which of the following statements is TRUE regarding observational studies?

Accepted Answer

Observational studies allow researchers to claim association, but not causation.

Question 13

In the rat experiment on radio-frequency radiation, what is the response variable?

Accepted Answer

Incidence of brain tumors in rats

Question 14

A study finds that seniors who get flu shots are less likely to be hospitalized for pneumonia. Which of the following best describes why this result may not imply causation?

Accepted Answer

There may be lurking variables, such as overall health, that affect both the likelihood of getting a flu shot and hospitalization risk.

Question 15

In the study about teaching methods for math, what is the explanatory variable?

Accepted Answer

Type of teaching method (traditional vs. reform)

Question 16

Which of the following best describes a lurking variable?

Accepted Answer

A variable not considered in the study that affects the response variable and is related to the explanatory variable.

Question 17

A study finds that adolescents with a TV in their bedroom have higher BMI, even after adjusting for socioeconomic status. What does 'adjusting for socioeconomic status' mean?

Accepted Answer

The researchers statistically controlled for socioeconomic status to reduce its influence on the results.

Question 18

Which scenario best illustrates confounding?

Accepted Answer

A study finds an association between two variables, but a third variable may be responsible for the observed effect.

Question 19

In the study about TVs in the bedroom and adolescent BMI, can we conclude that having a TV in the bedroom causes higher BMI? Why or why not?

Accepted Answer

No, because the study was observational and cannot establish causation.

Question 20

Which of the following is an example of a real-world lurking variable in a study examining the relationship between TV ownership and life expectancy?

Accepted Answer

Access to healthcare

Observational Studies vs. Designed Experiments: Identifying Variables and Understanding Confounding

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