Question 1

Which of the following best describes the main difference between bias and variability in the context of experimental design?

Accepted Answer

Bias is the tendency for results to differ systematically from the truth, while variability is the spread of results due to random chance.

Question 2

In a survey about attitudes toward statistics, 98% of students responded positively. Which type of bias is most likely to affect the validity of this result if students who dislike statistics are less likely to respond?

Accepted Answer

Nonresponse bias

Question 3

Why do statisticians prefer randomization in experimental design?

Accepted Answer

It avoids sampling bias.

Question 4

Which sampling design is most appropriate for ensuring that all subgroups of a population are represented in a sample?

Accepted Answer

Stratified random sample

Question 5

A researcher wants to study the effect of three pest management strategies (organic pesticide, synthetic pesticide, no pesticide) on three varieties of wheat. How many treatments are there in this factorial experiment?

Accepted Answer

9 treatments

Question 6

In the Women's Intervention Nutrition Study, what was the experimental unit?

Accepted Answer

Each individual woman participating in the study

Question 7

Which principle of experimental design is illustrated by assigning subjects to treatment groups using a random process?

Accepted Answer

Randomization

Question 8

A clinical trial is conducted to test a new drug. The researchers use a placebo that looks identical to the drug but contains no active ingredient. What is the main purpose of the placebo?

Accepted Answer

To control for psychological effects and blinding

Question 9

Which of the following is NOT a required principle for a well-designed experiment?

Accepted Answer

Blocking

Question 10

In a randomized comparative experiment, what is the main advantage of replication at the treatment level?

Accepted Answer

It allows for estimation of variability within treatment groups.

Question 11

A researcher divides subjects into groups based on age before randomly assigning treatments. What experimental design principle is being used?

Accepted Answer

Blocking

Question 12

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

Accepted Answer

Neither the subjects nor the researchers measuring the response know which treatment was assigned.

Question 13

In a field experiment, why might blocking be used?

Accepted Answer

To control for known sources of variability, such as soil type or location

Question 14

Which formula would you use to estimate the required sample size for a given error margin $$E in a $$simple random sample, assuming known population standard deviation $$\sigma$$ and confidence level $$z^*$$?

Accepted Answer

$$n = \dfrac{(z^*)^2$ \cdot \$$sigma^2$$}{E^2$}$$

Question 15

A researcher uses a standardized questionnaire to collect data. What type of bias is this most likely to reduce?

Accepted Answer

Response bias

Question 16

In a factorial experiment with Factor A (2 levels) and Factor B (3 levels), how many unique treatment combinations are possible?

Accepted Answer

6

Question 17

Which of the following is a key difference between observational and experimental studies?

Accepted Answer

Experimental studies involve manipulation of factors, while observational studies do not.

Question 18

In the Women's Intervention Nutrition Study, which statistical method was used to compare relapse-free survival between groups?

Accepted Answer

Kaplan-Meier analysis

Question 19

Which of the following is an example of a covariate in an experimental study?

Accepted Answer

A variable measured that may influence the response, such as age or baseline health status

Question 20

A researcher wants to reduce variability in an experiment. Which strategy is most effective?

Accepted Answer

Increase the sample size

Experimental Design and Sampling in Statistics: Bias, Variability, and Survey Methods

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