Ch. 7
What is the typical level of significance for a hypothesis test in behavioral research?
.05
A measure of the size of an effect in a population is called ______.
effect size
A researcher obtains z = 2.04 for a one-sample z test. What is the decision for this test at a .05 level of significance?
to reject the null hypothesis
Given the following values: mc024-1.jpg = 10, M = 8, mc024-2.jpg = 0.5, conduct a one-sample z test at a .05 level of significance. What is the decision for a two-tailed test?
to reject the null hypothesis
A researcher obtains z = 1.80 for a one-sample z test. What is the decision for this test at a .05 level of significance?
It depends on whether the test is one-tailed or two-tailed.
When reporting the results of a one-sample z test using APA format, the ______ does not need to be reported.
critical values
Increasing sample size will ______.
increase the power of the decision
A researcher conducts a study, but has low power to detect an effect. Which of the following is one way in which the research can increase power?
increase the sample size
Based on the effect size conventions, d = 0.60 is a ______.
medium effect size
A professor gives an exam in which the mean score is 78 points. She gives another exam to test whether or not scores change. In this example, the null hypothesis is ______.
micron = 78
Suppose a researcher wants to make sure that the probability of committing a Type I error is less than 5%. How can the researcher control for this?
set the alpha level at .05
The power of the decision-making process is ______.
the likelihood of rejecting a false null hypothesis
A method for testing a claim or hypothesis about a parameter in a population, using data measured in a sample, is called ______.
hypothesis testing
Based on the effect size conventions, d = 0.90 is a ______.
large effect size
The criterion for a decision regarding the value stated in a null hypothesis is set by the ______.
level of significance
A researcher believes that increasing attention given to children will improve mean academic performance. Therefore, the alternative hypothesis should be ______.
mean academic performance will increase
What are the two decisions that researchers can make in hypothesis testing?
retain or reject the null hypothesis
______ allows researchers to describe (1) how far mean scores have shifted in the population or (2) the percentage of variance that can be explained by a given variable.
Effect size
Which of the following statements regarding the null hypothesis is true?
The null hypothesis always makes statements about a population parameter.
If a researcher obtains a null finding, then what is the decision?
They correctly retained the null hypothesis.
Hypothesis testing is also called ______.
significance testing
Based on the effect size conventions, d = 0.18 is a ______.
small effect size
A researcher reports that scores were higher than the mean in the population, z = 1.60, p = .05 (d = .14). If this was a test at a .05 level of significance, then what value must be incorrectly reported?
the p value
A researcher obtains z = -6.45. What is the decision for a one-tailed test, upper-tail critical, at a .05 level of significance?
to retain the null hypothesis
A researcher obtains z = 1.45 for a one-sample z test. What is the decision for this test at a .05 level of significance?
to retain the null hypothesis
Given the following values: mc025-1.jpg = 6.0, M = 7.6, n = 36, mc025-2.jpg = 6, conduct a one-sample z test at a .05 level of significance. For a one-tailed test, upper-tail critical, what is the decision?
to retain the null hypothesis
A researcher reports that the size of an effect in some population is d = 0.88. Which of the following is an appropriate interpretation for d?
Mean scores shifted 0.88 standard deviations in the population.
A researcher reports the following result for a one-sample z test at a .05 level of significance: z = 1.88, p = -.06 (d = .25). Is this result significant?
No, the decision is to retain the null hypothesis
Is a one-sample z test reported differently for one-tailed and two-tailed tests?
No, the same values are reported.
A researcher reports that the standard deviation in Population A is mc039-1.jpg = 2.3 and the standard deviation in Population B is mc039-2.jpg = 4.3. Which population is associated with the highest power to detect an effect?
Population A
A researcher reports that the size of an effect in Population A is d = 0.10 and the effect size in Population B is d = 0.34. Which population is associated with greater power to detect an effect?
Population B
Which of the following is a scenario in which increasing sample size will increase power ______.
all of these (when the probability of a Type I error is small, when the effect size is large, when the effect size is small)
The one-sample z test is a hypothesis test used to test hypotheses ______.
concerning a single population with a known variance
A researcher obtains z = 3.98 for a one-sample z test. If her decision is to retain the null hypothesis, then what do you know about her decision?
Her decision resulted in a Type III error.
Which of the following best describes the p value?
It is a conditional probability.
A researcher selects a sample of 36 students from a school population with a mean IQ of 100 and standard deviation of 12. She determines that the mean IQ in this sample is 104. Assuming she computes a one-sample z test at a .05 level of significance, what is the decision for a two-tailed test?
Reject the null hypothesis; IQ scores in this sample are significantly higher than those in the population.
A researcher conducts two studies. Each study was a one-sample z test. Both studies placed the rejection region in both tails and measured the same sample mean. The beat level in Study 1 was larger than the beta level used in Study 2. Which study is associated with greater power to detect an effect?
Study 2
A researcher computes a one-sample z test in two studies. Both studies used the same alpha level, placed the rejection region in both tails, and measured the same sample mean. The researcher selects a sample of 30 participants in Study 1 and decides to retain the null hypothesis. She selects a sample of 60 participants in Study 2 and decides to reject the null hypothesis. Which of the following is the best explanation for why the decision was different in Study 1 and Study 2?
The different decisions in Study 1 and Study 2 are possible because the second test was associated with greater power to detect an effect.
A researcher computes a test statistic and finds that the p value for this test is .03. What does this result mean?
There is a 3% likelihood of obtaining the test statistic value, if the null were true.
A researcher directly controls for the probability of a ______, but does not directly control for the probability of a ______.
Type I error; Type II error
When a researcher decides to retain the null hypothesis because the rejection region was located in the wrong tail, this is called a ______.
Type III error
In hypothesis testing, a researcher's decision ______.
all of these (is based on a probability, depends on the level of significance for a hypothesis test, can be to retain or reject the null hypothesis)
If the value of the test statistic is in the rejection region, then ______.
all of these (p < .05, the decision is to reject the null hypothesis, the value of the test statistic is larger than the critical value)
Researchers state a level of significance in terms of an alpha level. The alpha level indicates ______.
all of these (the probability of committing a Type I error, the probability of incorrectly rejecting the null hypothesis, the probability value for the rejection region)
The probability of committing a Type I error is stated by ______ and the probability for committing a Type II error is stated by ______.
alpha; beta
Which of the following is not one of the four steps to hypothesis testing?
identify hypothetical data
In hypothesis testing, a researcher can never ______.
prove that his or her hypothesis is correct
In Step 2 of hypothesis testing, researchers state a level of significance to minimize the probability of ______.
rejecting a true null hypothesis
The first step to hypothesis testing requires that a researcher ______.
state the hypotheses
A professor finds that the average SAT score among all students attending his college is 1150 mc002-1.jpg 150 (mc002-2.jpg mc002-3.jpg mc002-4.jpg). He polls his class of 25 students and finds that the average SAT score is 1,200. Suppose he computes a one-sample z test at a .05 level of significance. What is his decision?
to reject the null hypothesis for an upper-tailed test, but to retain the null hypothesis for a two-tailed test