Data Analysis Exam III

η2 = 0.43 (large effect size)

A researcher reports a significant effect with t(14) = 3.24. Compute η2 for this result.

All of these

Researchers state a level of significance in terms of an alpha level. The alpha level indicates

True

The standard error of the mean is the standard deviation in a sampling distribution of sample means.

False

The z statistic measures the size of an effect in some population.

Sample variances

What values are distributed along the x-axis for a sampling distribution of the sample variance?

to reject the null hypothesis

Given the following values: μ = 10, M = 8, σM = 0.5, conduct a one-sample z test at a .05 level of significance. What is the decision for a two-tailed test?

Type I error; Type II error

A researcher directly controls for the probability of a ______, but does not directly control for the probability of a ______.

the p value or the test statistic

A researcher reports that scores were higher than the mean in the population, z = 1.60, p = .05 (d = 0.14). If this was a test at a .05 level of significance, then what value must be incorrectly reported?

.50 and equal to the probability of selecting a sample mean that is at most equal to the population mean

A researcher selects a sample of 49 participants from a population with a mean of 12 and a standard deviation of 3.5. What is the probability of selecting a sample mean that is at least equal to the population mean?

1,000,000

A researcher selects a sample of size 6 from a population of size 10. How many possible samples of this size can be selected using theoretical sampling?

None, both samples will have the same value for standard error.

A researcher selects two samples of 25 participants each. In the first sample, the population mean was 32 and the variance was 8. In the second sample, the population mean was 4 and the variance was 8. Which sample will be associated with a larger standard error of the mean?

True

A sample mean is not always equal to a population mean.

True

Normality is the assumption that data in the population are normally distributed.

True

One step to hypothesis testing is to set the criteria for a decision.

Positively skewed

Regardless of the shape of the distribution in the population, the sampling distribution of sample variances approximates a

False

Researchers typically sample with replacement, although the development of statistical theory was based on the use of sampling without replacement.

-1.711

State the critical value(s) for a t test using a .05 level of significance in the lower tail only: t(24).

False

There are 25 possible samples of size 5 that can be selected from a population of 2 people using theoretical sampling.

Researcher B

Two researchers (A and B) compute a one-sample t test. For both tests, the standard error is the same, but the mean difference between the sample and value stated in the null hypothesis is smaller for Researcher A. Which test is more likely to result in a decision to reject the null hypothesis?

It explains that a sampling distribution of possible sample means is approximately normally distributed, regardless of the shape of the distribution in the population.

What is the central limit theorem?

True

When scores are measured in a single group, the sample standard deviation is used as an estimate of the population standard deviation in the effect size formula for estimated Cohen's d.

Cohen's d

Which measure of effect size is most commonly reported with a t test?

to retain the null hypothesis

Given the following values: μ = 6.0, M = 7.6, n = 36, σ = 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?

No, the same values are reported.

Is a one-sample z test reported differently for one-tailed and two-tailed tests?

Because it makes little sense to report the size of an effect that you just concluded doesn't exist.

It is most appropriate to report effect size with a significant result. Why is it generally inappropriate to report effect size with nonsignificant results?

set the alpha level at .05

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?

equal to the population mean

The mean of the sampling distribution of sample means is

Effect size

A measure of the size of an effect in a population is called

One-sample t test

A researcher records the number of distracters (such as noises) that preschool-aged children ignore while watching a popular Sunday morning cartoon show. Assuming that the population variance is unknown, what type of t test is appropriate for this study?

Two-tailed test because the p value is equal to .05.

A researcher reports that stress levels among nurses are higher compared to stress levels in the general population, t(20) = 2.086, p = .05 (d = .12). Was this a one-tailed or a two-tailed test?

12% of the variability in marketing effectiveness can be accounted for by the new marketing strategy.

A researcher reports that the effectiveness of a new marketing campaign significantly increased sales compared with the previous campaign strategy, t(49) = 2.562, p < .05. Use η2 to interpret the effect size for this result.

d = 0.05; small effect size

A researcher reports that the mean time it takes to complete an experimental task is 1.4 ± 8.0 ( M ± SD) s. If the null hypothesis was that the mean equals 1.0, then what is the effect size for this test using estimated Cohen's d?

2.0

A researcher selects a sample of 121 participants from a population with a mean of 32 and a standard deviation of 22. What is the standard error of the mean?

31

A researcher selects a sample of 32 participants who are assigned to participate in a study with one group. What are the degrees of freedom for this test?

Reject the null hypothesis; IQ scores in this sample are significantly higher than those in the population.

A researcher selects a sample of 36 students from a school population with a mean IQ of 100 and a 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?

Sample 1

A researcher selects two samples of 64 participants each. In the first sample, the population mean was 10 and the variance was 16. In the second sample, the population mean was 25 and the variance was 9. Which sample will be associated with a larger standard error of the mean?

False

A t test is associated with N degrees of freedom.

True

A z transformation can be computed to locate sample means in a sampling distribution.

the population variance is unknown.

As a requirement for the t test, researchers compute any type of t test with samples selected from populations in which

False

As sample size decreases, the standard error also decreases.

True

Assuming that the rejection region is placed in the correct tail, the power of detecting an effect is larger for one-tailed tests compared with two-tailed tests.

Medium effect size

Based on the effect size conventions, d = 0.60 is a

Large effect size

Based on the effect size conventions, d = 0.90 is a

True

Cohen's d is a measure of how far mean scores have shifted in a population.

the likelihood of rejecting a false null hypothesis.

The power of the decision-making process is

True

The test statistic determines whether or not an effect exists in a population; effect size measures the size of an observed effect in a population.

experimental sampling

Which type of sampling is most often applied by researchers in the behavioral sciences?

Effect size

______ 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