Question 1

Which of the following best describes an observational study?

Accepted Answer

A study in which researchers collect information from reality without manipulating any variables.

Question 2

In a well-designed experiment, what is the primary purpose of random assignment?

Accepted Answer

To control for confounding variables and allow conclusions about cause and effect.

Question 3

Professor Villegas surveys former students about their attendance at the Math Center and compares their average grades. What type of study is this?

Accepted Answer

Observational study

Question 4

Which of the following is a valid conclusion from Professor Villegas' study?

Accepted Answer

Students who attended the Math Center had higher average grades in Statistics.

Question 5

What is the main difference between random assignment and random sampling?

Accepted Answer

Random assignment creates comparable groups for an experiment, while random sampling selects a representative sample from the population.

Question 6

In the context of an experiment, what is the purpose of a placebo?

Accepted Answer

To control for psychological effects that might influence the response variable.

Question 7

Which of the following best describes a double-blind experiment?

Accepted Answer

Neither the participants nor the administrators know who is receiving which treatment.

Question 8

Suppose a pharmaceutical company wants to test a new drug. They assign patients to either the new drug or a placebo group using a random number generator. What aspect of experimental design is being used?

Accepted Answer

Random assignment

Question 9

In Professor Villegas' study, what is the explanatory variable?

Accepted Answer

Whether or not the student attended the Math Center

Question 10

Which of the following could be a confounding variable in Professor Villegas' study?

Accepted Answer

The students' prior motivation or study habits

Question 11

A researcher wants to test if a new teaching method improves test scores. She randomly assigns half the class to use the new method and the other half to use the traditional method. What is the response variable?

Accepted Answer

The students' test scores

Question 12

Why is it important for a placebo to look and taste like the actual treatment in an experiment?

Accepted Answer

To prevent participants from knowing which group they are in, controlling for psychological effects.

Question 13

Which of the following statements about experiments and observational studies is correct?

Accepted Answer

Only experiments can establish a cause-and-effect relationship.

Question 14

A clinical trial is conducted to test a new vaccine. The study is double-blind and includes a placebo group. Which of the following best describes the control group?

Accepted Answer

The group that receives the placebo.

Question 15

Suppose a study finds that people who exercise regularly have lower rates of heart disease. Which of the following is a valid conclusion from an observational study?

Accepted Answer

There is an association between regular exercise and lower rates of heart disease.

Question 16

A researcher wants to control for the effect of age in a drug trial. She ensures that both the treatment and control groups have similar age distributions. What is this technique called?

Accepted Answer

Direct control

Question 17

In an experiment, why is it important to have both a control group and a treatment group?

Accepted Answer

To compare the effects of the treatment against no treatment or a placebo.

Question 18

A study finds that students who attend more review sessions tend to have higher grades. Which of the following is a possible confounding variable?

Accepted Answer

The students' prior academic ability.

Question 19

Which of the following best describes the placebo effect?

Accepted Answer

A psychological or physiological response to receiving a treatment that has no therapeutic value.

Question 20

A nutritionist wants to test if a new diet leads to weight loss. She recruits 100 volunteers and randomly assigns 50 to the new diet and 50 to their usual diet. After 3 months, she compares the average weight loss between the two groups. Which statistical concept is being applied to ensure the groups are comparable?

Accepted Answer

Random assignment

Observational Studies vs. Experiments in Statistics: Concepts and Applications

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