Question 1

If the alpha level is changed from 0.05 to 0.01, what effect does it have on beta?

Accepted Answer

Decreasing the alpha level would make it more difficult to reject the null hypothesis, and therefore increase the likelihood of a type II error (false negative) occurring, which is represented by beta.

Question 2

If alpha is 0.05 and obtained probability level is 0.01, you could be making a _________.

Accepted Answer

If alpha is 0.05 and obtained probability level is 0.01, it means that the obtained probability level is less than the alpha level (0.01 < 0.05). This indicates that the null hypothesis would be rejected, leading to a correct decision. However, it is possible that a Type I error (rejecting a true null hypothesis) has been made.

Question 3

If you retain the null hypothesis, you may be making _________.

Accepted Answer

Retaining the null hypothesis can lead to a Type II error if the null hypothesis is false but is not rejected. It can also be a correct decision if the null hypothesis is true.

Question 4

The null hypothesis which is appropriate for a directional alternative hypothesis asserts that _________.

Accepted Answer

A directional alternative hypothesis makes a prediction about the direction of the effect. Therefore, the appropriate null hypothesis would be that the independent variable does not have an effect in the direction predicted by H1. Option A refers to a non-directional alternative hypothesis, while B refers to a general null hypothesis. Option D is incorrect because while option B is partially correct, option C is the more appropriate choice.

Question 5

If we set alpha at 0.05 instead of 0.01 _________.

Accepted Answer

Setting alpha at 0.05 instead of 0.01 increases the risk of a Type I error (rejecting a true null hypothesis) because we are more willing to accept evidence against the null hypothesis. Conversely, it decreases the risk of a Type II error (failing to reject a false null hypothesis) because we are more likely to detect an effect if one truly exists.

Question 6

It is important to know the possible errors (Type I or Type II) we might make when rejecting or retaining H 0 _________.

Accepted Answer

It is important to know the possible errors to minimize these errors when designing the experiment (A), to be aware of the fallacy of "accepting H 0 " (B), and to maximize the probability of making a correct decision by proper design (C). Therefore, all of these options are correct.

Question 7

When the results of an experiment are nonsignificant, the proper conclusion(s) is (are) _________.

Accepted Answer

A nonsignificant result means that the experiment did not provide enough evidence to reject the null hypothesis, suggesting that the experiment fails to show a real effect for the independent variable. However, it does not prove that the independent variable has no effect or that chance alone is at work.

Question 8

In stating H 0 and H 1 , one must be certain that they are _________.

Accepted Answer

H0 (null hypothesis) and H1 (alternative hypothesis) must be mutually exclusive, meaning they cannot both be true at the same time, and exhaustive, covering all possible outcomes.

Question 9

If you reject the null hypothesis, you may be making _________.

Accepted Answer

If you reject the null hypothesis, you may be making a Type I error (rejecting a true null hypothesis) or a correct decision (rejecting a false null hypothesis). There is no possibility of making a Type II error if you reject the null hypothesis.

Question 10

Using the sign test, if the null hypothesis is false, then P (the probability of a plus) _________.

Accepted Answer

The sign test is a non-parametric test used to determine whether two groups are statistically different from each other. It compares the number of observations in two groups that are greater or less than a specified value. If the null hypothesis is false, then the probability of a plus (or minus) sign will be different from 0.50. This means that the number of observations in one group is significantly different from the other group. Therefore, the correct answer is D, which states that P is not equal to 0.50.

Question 11

lf alpha is changed from 0.05 to 0.01, _________.

Accepted Answer

When alpha is decreased from 0.05 to 0.01, we are increasing the threshold for rejecting the null hypothesis. This makes it less likely for us to reject the null hypothesis when it is actually true, thus increasing the probability that we will retain a false null hypothesis (Type II error).

Question 12

In the repeated measures design, _________.

Accepted Answer

In a repeated measures design, the same participants are tested in different conditions or at different time points, so differences between paired scores are analyzed to assess the effect of the manipulation or intervention. Raw scores in each condition are not analyzed separately as the focus is on the change from one condition to the next. A directional alternative hypothesis may or may not be used, depending on the research question and design. Therefore, only option A is correct.

Question 13

In an experiment with a repeated measures design _________.

Accepted Answer

In a repeated measures design, the same subjects are used in both treatment groups, which allows for greater control over individual differences and increases the power of the experiment. Option A is incorrect because the experiment is not repeated in its entirety, just the treatment is repeated. Option B is referring to an independent measures design, where two different groups receive different treatments. Option D is incorrect because there is an experimental design being described here.

Question 14

The statistic used in the sign test measures _________.

Accepted Answer

The sign test measures the direction of the differences between pairs of scores. It looks at whether one group has higher or lower scores than the other group, without considering the magnitude of the differences.

Question 15

The nondirectional alternative hypothesis asserts that _________.

Accepted Answer

The nondirectional alternative hypothesis states that the independent variable has an effect, but it does not specify the direction of the effect. This means that the results could show an increase, a decrease, or simply a difference between groups, but the hypothesis asserts that the independent variable does have an effect on the dependent variable.

Question 16

An alpha level of 0.05 indicates that _________.

Accepted Answer

An alpha level of 0.05 sets the level of significance at 5%, meaning that if the null hypothesis is true, there is a 5% chance of falsely rejecting it (also known as a Type I error). This is why option A is the correct answer. Option B is incorrect because an alpha level of 0.05 doesn't tell us anything about the percentage of times chance is operating. Option C is incorrect because the probability of a Type II error is not the same as the alpha level. Option D is incorrect because the alpha level is not directly related to the probability of a correct decision.

Question 17

If alpha equals 0.05 and the probability level of your experiment is 0.04, you would _________.

Accepted Answer

In hypothesis testing, we compare the probability level (p-value) of our experiment to the pre-determined alpha level. If the p-value is smaller than the alpha level, we reject the null hypothesis. In this case, the probability level is 0.04 which is smaller than the alpha level of 0.05. Therefore, we reject the null hypothesis.

Question 18

In an experiment involving a nondirectional alternative hypothesis, the obtained result was 7 pluses and 1 minus. To evaluate the null hypothesis, which of the following probabilities would you use?

Accepted Answer

In a nondirectional alternative hypothesis, the researcher is interested in deviations from the null hypothesis in either direction. Therefore, to evaluate the null hypothesis, we need to consider the probability of obtaining an outcome as extreme or more extreme than the one observed (i.e., 7 pluses and 1 minus) both in the positive and negative directions.

Option A only considers the probability of obtaining 7 pluses, ignoring the possibility of obtaining 1 minus. Option B includes the probability of obtaining 8 pluses, which is even more extreme than the observed outcome. Option D only considers the probability of obtaining 1 minus and 7 pluses in the specific configuration observed, ignoring other possible configurations.

Option C is the best choice because it includes the probabilities of obtaining 0, 1, 7, and 8 pluses, which encompasses all possible outcomes as extreme or more extreme than the one observed in both directions.

Question 19

If the alternative hypothesis states that alcohol affects short-term memory, the null hypothesis states _________.

Accepted Answer

The null hypothesis is typically a statement that the treatment or factor being tested has no effect. In this case, the null hypothesis would be that alcohol has no effect on short-term memory. Therefore, option B is the correct answer. Option A is the opposite of the alternative hypothesis and option C is a directional hypothesis, which is not appropriate for a null hypothesis. Option D is not relevant to this scenario.

Question 20

In the sign test, if the null hypothesis is true, then P _________.

Accepted Answer

The sign test is a non-parametric test that compares two dependent samples to determine if there is a significant difference between them. It is based on the number of positive and negative differences between the pairs of observations. If the null hypothesis is true, then the probability of a positive difference is equal to the probability of a negative difference, which is 0.50. Therefore, the answer is A.

Quiz 10: Introduction to Hypothesis Testing: Using the Sign Test