Question 1

The effect size and the number of participants are two important determinants of

Accepted Answer

Power is the probability of correctly rejecting a false null hypothesis. It depends on the effect size (the magnitude of the difference or relationship between groups or variables) and the sample size (number of participants). A larger effect size or larger sample size leads to greater power, meaning the study is more likely to detect a significant effect if it exists. The minimum significant result and alpha are determined by the researcher, while experimental significance is the same as statistical significance and is based on the p-value.

Question 2

Power is the probability that

Accepted Answer

Power is the probability that the experiment will support the research hypothesis, which means that if the research hypothesis is true, the experiment will support it.

Question 3

In actual practice,the usual reason for determining power before conducting a study is

Accepted Answer

Determining power before conducting a study is typically done to determine the number of participants needed to have a reasonable level of power. In other words, it is important to have enough participants in a study to ensure that the study has the ability to detect a significant effect if one exists. This helps to ensure that the study is not underpowered, which could result in a failure to detect a significant effect even if one exists.

Question 4

If the effect size and the desired level of power are known,the power formula can be used to determine the

Accepted Answer

The power formula can be used to calculate the number of participants needed for a study, given the effect size and desired level of power. The minimum meaningful difference is typically determined based on prior research or expert opinion, and is not directly calculated using the power formula. Population distribution and alpha level are also not directly determined by the power formula.

Question 5

When conducting an experiment with 95% power,failing to reject the null hypothesis means that

Accepted Answer

The statement in D correctly interprets the scenario of not rejecting the null hypothesis in an experiment with 95% power. It means that there is less than a 5% chance that the observed data would occur if there were a true difference between populations larger than the one specified when calculating the experiment's power. This does not confirm the null hypothesis as true (C), nor does it necessarily indicate a poorly conducted experiment (B) or that there is no difference at all (A).

Question 6

If an experimenter CANNOT manipulate the effect size of an experiment to increase power,the aspect of a study that can usually be changed easily to increase power is

Accepted Answer

The sample size is the aspect of a study that can be easily changed to increase power. Increasing sample size in a study can lead to a larger effect size and increased power, even if the effect size cannot be manipulated by the experimenter. Beta level refers to the probability of making a Type II error, which is not directly related to power. Population parameters and sample mean are fixed values that cannot be changed once the sample has been collected.

Question 7

Cohen's (1962)review of power in psychological studies revealed that

Accepted Answer

Cohen's review highlighted that no study had power greater than 50%, indicating a significant issue with the statistical power in psychological research at the time. This low power means that many studies had a high risk of failing to detect true effects when they exist.

Question 8

The statistical method currently used to combine the results of multiple studies is

Accepted Answer

Meta-analysis is the statistical method used to combine the results of multiple studies. It involves a systematic review of current literature and a quantitative analysis of the results to determine the strength and accuracy of the findings. Power analysis, regression analysis, and retrospective analysis are all separate statistical methods and do not involve the combination of multiple studies.

Question 9

The probability of NOT making a Type II error is

Accepted Answer

The probability of not making a Type II error is known as the power of a statistical test. This represents the test's ability to correctly reject a false null hypothesis.

Question 10

If a study conducted at the .05 significance level has 80% power

Accepted Answer

In statistical hypothesis testing, the significance level (alpha) is the probability of rejecting the null hypothesis when it is true, set at 5% in this case. Power is the probability of correctly rejecting the null hypothesis when it is false, which is 80%. Beta is the probability of failing to reject the null hypothesis when it is false, which is 100% - 80% = 20%. Therefore, the correct answer is B) alpha = 5%, beta = 20%.

Question 11

A psychologist conducts a study and finds that d = -.63.This effect size would most likely be described as

Accepted Answer

The answer of A psychologist conducts a study and finds...

Question 12

Some psychologists have argued that simple significance tests are misleading,and that a better statistic to evaluate the outcome of an experiment would be the

Accepted Answer

Effect size is a better statistic to evaluate the outcome of an experiment because it provides information about the magnitude of the effect of the independent variable on the dependent variable, rather than just indicating whether the effect is statistically significant or not. This information is important for determining the practical significance of the result and its relevance for real-world situations.

Question 13

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

Accepted Answer

Effect size indicates the size of the statistical effect, allowing researchers to determine the practical significance of their results beyond just statistical significance.

Question 14

If the research hypothesis is true but the study has a low level of power,then

Accepted Answer

If the study has a low level of power, it means that the probability of detecting a true effect is low. Therefore, even if the research hypothesis is true, the probability that the study will have a significant result is also low. This increases the likelihood of a Type II error, where a true effect is not detected.

Question 15

When the standard deviation of the original population is small,the experiment tends to

Accepted Answer

A small standard deviation indicates that the data points are clustered closely around the mean, making it easier to detect a significant difference between the two groups. This means that the experiment will tend to have a higher level of power, which is the ability to detect a true difference between the groups. A lower level of power would occur if there is a large amount of variability in the data, which makes it harder to distinguish between the two populations. A less significant difference between the two populations would occur if the means are close together, regardless of the standard deviation. Type II error is not directly related to the standard deviation but rather the sample size and significance level chosen for the experiment.

Question 16

While no research hypothesis is ever definitely false,failing to reject the null hypothesis in a study that has a high level of power allows one to

Accepted Answer

A study with high statistical power means that it is highly likely to detect an effect if there is one. Therefore, if such a study fails to reject the null hypothesis, it suggests that the research hypothesis (which posits that there is an effect) is most likely false. This is because the study was well-equipped to find evidence of the effect but did not.

Question 17

Effect size is one of the two major factors that contribute to power; the other factor is

Accepted Answer

The sample size is the other major factor that contributes to power along with effect size. Sample size determines the precision of an estimate, making it easier to detect small effects with larger samples. Therefore, C is the best choice. A, B, and D are incorrect because they are not major factors that contribute to power.

Question 18

Standard power tables are useful for

Accepted Answer

Standard power tables are used to directly determine the power of an experiment. Power tables provide information about the minimum sample size required to achieve a desired level of power.

Question 19

James asks his friend Rob for advice on how to increase the power of his experiment.Which of Rob's suggestions is incorrect?

Accepted Answer

Using a two-tailed instead of a one-tailed test does not increase the power of an experiment. Instead, it is more conservative, requiring more evidence to reject the null hypothesis, as it tests for the possibility of an effect in two directions rather than one.

Question 20

A psychologist conducts a study and finds that d = 1.41.This effect size would most likely be described as

Accepted Answer

A d value of 1.41 indicates a large effect size. Cohen's d effect sizes are typically classified as small (d = 0.2), medium (d = 0.5), or large (d = 0.8 or higher), so a d value of 1.41 falls in the large category.

Quiz 6: Making Sense of Statistical Significance:decision Errors, Effect Size, and Statistical Power