Question 1

Which of the following best describes a confidence interval?

Accepted Answer

An interval estimate that includes the mean expected for the sample statistic a certain percentage of the time, if the same population is sampled repeatedly.

Question 2

What is the formula for calculating the lower bound of a confidence interval for a z test?

Accepted Answer

$$M_{lower} = -z (\sigma_M) + M_{sample}$$

Question 3

Why does increasing sample size make it more likely to find a statistically significant effect?

Accepted Answer

It always increases the test statistic if all else stays the same.

Question 4

Which of the following is NOT a property of effect size?

Accepted Answer

It determines the probability of a Type I error.

Question 5

Cohen's d is calculated using which formula?

Accepted Answer

$$d = \frac{M - \mu}{\sigma}$$

Question 6

Meta-analysis provides added statistical power by:

Accepted Answer

Considering multiple studies simultaneously.

Question 7

Which step is NOT part of the meta-analysis process?

Accepted Answer

Ignore studies with null results.

Question 8

The 'file drawer' analysis is used to:

Accepted Answer

Determine how many studies with null results would be needed to make a mean effect size non-significant.

Question 9

Statistical power is best defined as:

Accepted Answer

The likelihood of rejecting the null hypothesis, given that the null is false.

Question 10

Which of the following factors does NOT increase statistical power?

Accepted Answer

Decreasing the mean difference between levels of the independent variable.

Question 11

A researcher wants to increase the effect size in their study. Which strategy would be most effective?

Accepted Answer

Decrease the variation within each population.

Question 12

If a study fails to reject the null hypothesis when the null is actually false, what type of error has occurred?

Accepted Answer

Type II error (false negative)

Question 13

Which of the following is a benefit of using confidence intervals in research?

Accepted Answer

They confirm findings of hypothesis testing and add more detail.

Question 14

A 95% confidence interval means that:

Accepted Answer

If the same population is sampled repeatedly, the interval will include the mean expected for the sample statistic 95% of the time.

Question 15

In the context of gender differences in mathematics performance, meta-analysis by Hyde, Fennema, & Lamon (1990) found that:

Accepted Answer

Mean gender differences in mathematical reasoning were very small.

Question 16

Which equation is used to calculate the z statistic for a sample mean?

Accepted Answer

$$z = \frac{M - \mu_M}{\sigma_M}$$

Question 17

Turning a two-tailed hypothesis into a one-tailed hypothesis affects statistical power by:

Accepted Answer

Increasing statistical power.

Question 18

Which of the following is a step in calculating statistical power?

Accepted Answer

Determine a critical z value and raw mean to calculate power.

Question 19

Why is it important to know the statistical power of your study?

Accepted Answer

To determine the likelihood of correctly rejecting the null hypothesis when it is false.

Question 20

Which of the following conventions for Cohen's d indicates a large effect size?

Accepted Answer

0.8

Confidence Intervals, Effect Size, and Statistical Power – Study Notes

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