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

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Question 1

Multiple Choice

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The alpha level is

A) usually determined while analyzing experimental data.
B) the chance of obtaining an inconclusive result when the research hypothesis is true.
C) the probability of a Type I error.
D) always set at 1%.

E) C) and D)
F) None of the above

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Question 2

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Setting the significance level at .20 increases the chance of

A) obtaining a nonsignificant result.
B) failing to reject the null hypothesis.
C) a Type I error.
D) a Type II error.

E) A) and B)
F) A) and C)

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Question 3

Multiple Choice

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Power is the probability that

If power is 45%,then beta equals __________.

Using the .01 level of significance instead of the .05 level increases the chance of making a(n)__________.

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

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

A way to increase effect size is to change the procedures of a study so that the __________ of the population is decreased.

When the known and comparison populations overlap by 85%,the effect size is __________.

According to Cohen,a good general rule for when it is worthwhile to conduct a study is when power is at least __________%.

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

Increasing sample size __________ power.

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

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

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

An organizational psychologist conducted a study to see whether upgrading a company's older computer system to newly released,faster machines would cause an increase in productivity from the current average of 120 units with a standard deviation of 20.The new system will be tested in a single department with 45 employees.The company has decided that an increase of less than 10 units will not justify purchasing the new system. a.What is the predicted effect size for an increase of 10 points? b.Explain the logic of what has been done. c.Advanced topic: Sketch the distributions involved. d.Advanced topic: If the data are analyzed at the .01 significance level,what will be the power of the study? e.Advanced topic: Explain your answer to a person who understands hypothesis testing with means of samples,but who is not familiar with power.

The smaller the population standard deviation,the greater the power,because the distributions of means based on the known and comparison populations are both __________.

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

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

The degree of separation between populations due to the independent variable is one way of understanding __________.