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Statistics for the Behavioral Sciences by Frederick J. Gravetter, Larry B. Wallnau ISBN 10: 1305504917 ISBN 13: 9781305504912

Statistics is one of the most practical and essential courses that you will take, and a primary goal of this popular text is to make the task of learning statistics as simple as possible. Straightforward instruction, built-in learning aids, and real-world examples have made STATISTICS FOR THE BEHAVIORAL SCIENCES, 10th Edition the text selected most often by instructors for their students in the behavioral and social sciences. The authors provide a conceptual context that makes it easier to learn formulas and procedures, explaining why procedures were developed and when they should be used. This text will also instill the basic principles of objectivity and logic that are essential for science and valuable in everyday life, making it a useful reference long after you complete the course.

Statistics is one of the most practical and essential courses that you will take, and a primary goal of this popular text is to make the task of learning statistics as simple as possible. Straightforward instruction, built-in learning aids, and real-world examples have made STATISTICS FOR THE BEHAVIORAL SCIENCES, 10th Edition the text selected most often by instructors for their students in the behavioral and social sciences. The authors provide a conceptual context that makes it easier to learn formulas and procedures, explaining why procedures were developed and when they should be used. This text will also instill the basic principles of objectivity and logic that are essential for science and valuable in everyday life, making it a useful reference long after you complete the course.

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SECTION 8.4 | Directional (One-Tailed) Hypothesis Tests 245

LEARNING CHECK

1. A research report summarizes the results of the hypothesis test by stating, “z = 2.13,

p < .05.” Which of the following is a correct interpretation of this report?

a. The null hypothesis was rejected and the probability of a Type I error is less

than .05.

b. The null hypothesis was rejected and the probability of a Type II error is less

than .05.

c. The null hypothesis was not rejected and the probability of a Type I error is less

than .05.

d. The null hypothesis was not rejected and the probability of a Type II error is less

than .05.

2. Which of the following is not an assumption for the z-score hypothesis test?

a. The observations must be independent.

b. The value for μ must be the same after treatment as it was before treatment.

c. The value for σ must be the same after treatment as it was before treatment.

d. The sample must be obtained by random sampling.

3. A sample of n = 16 individuals is selected from a population with µ = 80 and σ = 5,

and a treatment is administered to the sample. If the treatment really does have an

effect, then what would be the effect of increasing the standard deviation to σ = 25?

a. Increase the chances that the sample will produce an extreme z-score and

increase the likelihood that you will conclude that a treatment effect exists.

b. Increase the chances that the sample will produce an extreme z-score and

increase the likelihood that you will conclude that a treatment effect does

not exist.

c. Increase the chances that the sample will produce a z-score near zero and

increase the likelihood that you will conclude that a treatment effect exists.

d. Increase the chances that the sample will produce a z-score near zero and increase

the likelihood that you will conclude that a treatment effect does not exist.

ANSWERS

1. A, 2. B, 3. D

8.4 Directional (One-Tailed) Hypothesis Tests

LEARNING OBJECTIVE

9. Describe the hypotheses and the critical region for a directional (one-tailed)

hypothesis test.

The hypothesis-testing procedure presented in Sections 8.2 and 8.3 is the standard, or

two-tailed, test format. The term two-tailed comes from the fact that the critical region

is divided between the two tails of the distribution. This format is by far the most widely

accepted procedure for hypothesis testing. Nonetheless, there is an alternative that is

discussed in this section.

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