Question 1

Which of the following best describes a null hypothesis in experimental design?

Accepted Answer

A statement that there is no effect or difference between groups.

Question 2

A researcher wants to compare the mean blood pressure between two independent groups. Which statistical test should they use?

Accepted Answer

Unpaired t-test

Question 3

Which of the following is a key feature of a controlled experiment?

Accepted Answer

Only one variable is manipulated while all others are kept constant.

Question 4

If a p-value is less than 0.05, what does this indicate about the null hypothesis?

Accepted Answer

The null hypothesis should be rejected.

Question 5

Which formula correctly represents the calculation of the mean ($$\mu) of a $$data set with $$n$$ values $$x_1$$, $$x_2$$, ..., x_n$$?

Accepted Answer

$$ \mu = \frac{\sum_{i=1}^{n} x_i}{n} $$

Question 6

A scientist collects paired data from the same subjects before and after a treatment. Which statistical test is most appropriate?

Accepted Answer

Paired t-test

Question 7

Which of the following is NOT a requirement for a valid scientific hypothesis?

Accepted Answer

It must be proven true.

Question 8

What is the main purpose of randomization in experimental design?

Accepted Answer

To eliminate bias and evenly distribute confounding variables.

Question 9

Which of the following best describes a Type I error?

Accepted Answer

Rejecting a true null hypothesis.

Question 10

Given the following data set: 2, 4, 4, 6, 8. What is the standard deviation ($$s$$)? Use the formula $$ s = \sqrt{\frac{\sum (x_i - \bar{x})^2$}{n-1}} .$$

Accepted Answer

$$ s = 2.24 $$

Question 11

Which statistical test would be most appropriate for comparing the means of three or more independent groups?

Accepted Answer

ANOVA

Question 12

A researcher finds a correlation coefficient $$r = 0.85$$ between two variables. What does this indicate?

Accepted Answer

A strong positive linear relationship.

Question 13

Which of the following is an example of a categorical variable?

Accepted Answer

Blood type (A, B, AB, O)

Question 14

If the results of an experiment are not statistically significant, what is the most appropriate conclusion?

Accepted Answer

There is not enough evidence to reject the null hypothesis.

Question 15

Which of the following best describes the purpose of a control group in an experiment?

Accepted Answer

To provide a baseline for comparison.

Question 16

A scientist wants to test if a new drug lowers cholesterol more than a placebo. Which is the null hypothesis?

Accepted Answer

There is no difference in cholesterol levels between the drug and placebo groups.

Question 17

Which of the following is a continuous variable?

Accepted Answer

Body temperature in $$^ C$$

Question 18

Which of the following is the correct formula for calculating the standard error of the mean (SEM)?

Accepted Answer

$$ SEM = \frac{s}{\sqrt{n}} $$

Question 19

A study finds a p-value of 0.07. What does this mean in the context of a significance level of 0.05?

Accepted Answer

There is weak evidence against the null hypothesis.

Question 20

Which of the following best describes the difference between accuracy and precision in scientific measurements?

Accepted Answer

Accuracy is how close measurements are to the true value; precision is how close measurements are to each other.

Scientific Skills & Statistics: Experimental Design and Data Analysis

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