Question 1

One way of understanding __________ is in terms of the degree of separation between populations due to the experimental variable.

Accepted Answer

The answer of One way of understanding __________ is in...

Question 2

The __________ of a study is the difference in the population means divided by the population SD.

Accepted Answer

The answer of The __________ of a study is the...

Question 3

According to Cohen, for an experiment to be worth conducting, it should have a level of power of about:

Accepted Answer

Cohen suggests that an experiment should have a power of at least 80%, so choice C is the correct answer. Any lower power level would indicate that the experiment is not able to detect a significant effect even if one exists, which renders the results inconclusive or unreliable. On the other hand, a power level of near 100% is unrealistic and unnecessary, as it would require an extremely large sample size and heightened control, which are not always practical or feasible in research. Therefore, the best choice is C.

Question 4

If the results of a study are not statistically significant and the sample size is large, then:

Accepted Answer

If the results of a study are not statistically significant and the sample size is large, it suggests that the observed effect is likely due to chance variation, and the research hypothesis is probably false. A large sample size increases the power of the study, so if the result is still not significant, it implies that the effect is not large enough to be practically important or meaningful. The null hypothesis is not necessarily proven, but rather not rejected due to lack of strong evidence against it. Therefore, choice C is the correct response.

Question 5

The __________ is a statistic that combines two of the main influences on power, the expected difference between populations and the population standard deviation.

Accepted Answer

The answer of The __________ is a statistic that combines...

Question 6

For a particular research study, simply knowing about __________ does not provide much information about the size of the effect.

Accepted Answer

The answer of For a particular research study, simply knowing...

Question 7

When judging a study's results, there are two important questions. They are:

Accepted Answer

The two important questions when judging a study's results are whether the result is statistically significant and whether the effect size is large enough for the results to be meaningful. These questions are answered by the p-value (significance level) and effect size, respectively. The power and competence of the researchers, whether the significance level is stringent enough, and the replicability of the study are also important factors to consider, but they are not the two most important questions when judging a study's results.

Question 8

Knowing the effect size of a study lets you compare results with effect sizes found in other studies, but only when the other studies have equal sample sizes. (True or False)

Accepted Answer

Effect sizes can be compared across studies of different sizes using standardized effect sizes such as Cohen's d or Pearson's r.

Question 9

If a study with only a few participants manages to be statistically significant, it probably had:

Accepted Answer

A large effect size means that the treatment or intervention had a significant impact on the outcome being measured, which can produce significant results even with a small sample size.

Question 10

What is the most likely explanation for why a study with a very small effect size came out significant?

Accepted Answer

With a large sample size, even a small effect size can become statistically significant due to the reduction in standard error.

Question 11

One way of decreasing the standard deviation of the distribution of means in a planned study, thereby increasing power, is to have a larger number of participants. Another would be to:

Accepted Answer

Using a less diverse population reduces the variability within the data, which in turn decreases the standard deviation of the distribution of means. This can increase the statistical power of a study by making it easier to detect a true effect, if one exists.

Question 12

In order to convert a raw score effect size to a standardized effect size, one should:

Accepted Answer

The answer of In order to convert a raw score...

Question 13

Effect size is a standardized measure of difference (lack of overlap)between populations. (True or False)

Accepted Answer

Effect size is a standardized measure of difference between populations, which takes into account the variability within the populations being compared. It is calculated as the difference in means (or proportions) between groups divided by the standard deviation of the population. This standardized measure allows for easier comparison across studies and can help determine the clinical or practical significance of a particular finding.

Question 14

Effect size is an important tool for making sense of research results because:

Accepted Answer

Effect size tells us the magnitude of the statistical effect, which is important for understanding the practical significance of the results. The degree of statistical significance (A) is important but does not tell us about the magnitude of the effect. Effect size does not limit variance or increase power (C) and it is not always smaller than the variance (D).

Question 15

Practical significance is a combination of statistical significance and:

Accepted Answer

Practical significance takes into account both statistical significance and the effect size, which represents the magnitude of the difference or relationship between two groups or variables. The level of measurement, population parameters, and the amount over or under the level that the sample scored may be important considerations in other aspects of statistical analysis, but they are not directly related to practical significance.

Question 16

The effect size of a study is a good indicator of its practical importance because, unlike statistical significance, it is not affected by __________.

Accepted Answer

The answer of The effect size of a study is...

Question 17

What does it mean to say "A between-groups effect size of .6 was achieved for the treatment group as compared to the no-treatment group"?

Accepted Answer

The term "between-groups effect size" means comparing the difference in scores or outcomes between two groups. An effect size of .6 indicates that the treatment group was .6 standard deviations higher on the outcome than the no-treatment group.

Question 18

In statistics, we cannot state that the research hypothesis is ever definitely false. However, if one fails to reject the null hypothesis in a study with a high level of power, this allows us to:

Accepted Answer

Failing to reject the null hypothesis in a study with high power suggests that the research hypothesis is most likely false because high power means there was a good chance of detecting an effect if one existed.

Question 19

Effect Size = (Population 1M - Population 2M)/__________.

Accepted Answer

The answer of Effect Size = (Population 1M - Population...

Question 20

Changing the procedures of a study so that it decreases the __________ of the population increases the effect size.

Accepted Answer

The answer of Changing the procedures of a study so...

Quiz 7: Making Sense of Statistical Significance: Effect Size and Statistical Power