The One Sample T-Test

A social psychologist wishes to understand if children in a single-parent household, where that parent is deaf, use more gestures than their peers. What effect size will be required to reach a power level of .80 in a two-tailed study design if α is set to .05 and the sample size is 15? a. 0.52 b. 0.56 c. 0.78 d. 0.64

0.78

A researcher is investigating how social interactions with neighborhood pets affects a person's stress. With α set at .05, effect size is predicted to be 0.5, and power set to .85 to reduce the Type II error. What sample size will be needed if the researcher is planning a two-tailed study design? a. 21 b. 156 c. 36 d. 38

38

For a group of n = 35 undergraduate students, the sample mean score was 82.3, while the expected mean was 80.0. Which of the following confidence intervals would be associated with a decision to reject the null hypothesis for a two-tailed test (α = .05)? a. 95% CI = [80.4, 84.2] b. 95% CI = [79.8, 84.8] c. 95% CI = [78.7, 85.9] d. 95% CI = [79.1, 85.5]

95% CI = [80.4, 84.2]

Select the statement that is true regarding when to use a one-sample t-test. a. A one-sample t-test is appropriate when both the sample mean and the sample standard deviation are unknown. b. A one-sample t-test is appropriate when the sample standard deviation is unknown. c. A one-sample t-test is appropriate when both the population mean and the population standard deviation are unknown. d. A one-sample t-test is appropriate when the population mean is known, but the population standard deviation is unknown.

A one-sample t-test is appropriate when the population mean is known, but the population standard deviation is unknown.

Which of the curves would have the least variability? a. A z-distribution b. Variability is equal for all of these. c. A t-distribution for n = 3 d. A t-distribution for n = 15

A z-distribution

For a power curve with power on the y-axis and effect size on the x-axis, how does effect size change as power increases? a. Effect size does not change with power. b. Effect size increases as power increases. c. Effect size decreases as power increases. d. Effect size increases as power decreases.

Effect size increases as power increases.

A researcher wanted to compare the average Graduate Record Examination (GRE) scores for a sample of 15 college seniors in the social sciences to the average GRE for all test-takers in the United States. Because the GRE is a standardized test, the mean and standard deviation are known. Is a one-sample t-test the best statistical test for this analysis? a. Yes, because both the population mean and standard deviation are known. b. No, because the sample size is not over 30. c. Yes, because the sample size is small. d. No, because the population standard deviation is known.

No, because the population standard deviation is known.

How does a t-distribution for n = 2 look different from the z-distribution? a. The t-distribution would not be symmetric. b. The two distributions would not look different. c. The t-distribution would have more values in the middle of the distribution. d. The t-distribution would have more values in the tails of the distribution.

The t-distribution would have more values in the tails of the distribution.

After conducting a two-tailed one-sample t-test with α = .05, the researcher summarized the results as t(28) = 1.43, p > .05. Which of the following is a correct interpretation of these results? a. The difference was 1.43 standard deviations, which is a large difference. b. The difference is statistically significant because 1.43 is in the rejection region. c. There were 28 participants in the study and the difference was statistically significant. d. There were 29 participants in the study and the difference was not statistically significant.

There were 29 participants in the study and the difference was not statistically significant.

When does a t-distribution resemble a z-distribution? a. t-distributions never resemble a z-distribution b. When sample size is small c. When sample size is very large d. When there is a large population standard deviation

When sample size is very large

In a study of the time-course of the common cold, an experimental group of participants was infected with a cold virus, while a control group was not. Using the value of 99.5°F as an operational definition of "fever," the researchers tested the groups after 24 hours and found that the mean experimental group temperature was 99.9°F (n = 24). For a one-tailed t-test conducted to determine whether the experimental group exceeded the designated criteria for "fever," with α = .05, the it-statistic was 2.25. Was the difference statistically significant? a. Yes, because the t-statistic was located in the rejection region. b. Yes, because the t-statistic was close to 0. c. No, because the associated p-level of the t-statistic was > .05. d. No, because the t-statistic was not located in the rejection region.

Yes, because the t-statistic was located in the rejection region.

Which of these four values is set by convention in psychological research and not typically open to change by the researcher? a. n b. α c. d d. σ

a

Confidence intervals provide: a. an interval estimate for the population. b. the precise range for the population mean. c. an effect size estimate for a hypothesis test. d. the probability of obtaining a specific sample mean.

an interval estimate for the population.

A researcher is measuring activity level in a sample of adults following a seminar on health and fitness. She would like to compare the average activity level of her sample, measured in minutes per week, to that of the recommended average activity level for adults in the United States to discuss the size of the difference. Which of the following would provide that information? a. Effect size b. One-sample t-test c. Confidence interval d. Standard error of the mean

effect size

When the population standard deviation is known, the ____ is the appropriate test; when the population standard deviation is not known, the ____ is the appropriate test. a. z-test; t-test b. σ-test; t-test c. t-test; z-test d. t-test; σ-test

z-test; t-test

An instructor compared the average weekly minutes spent reading an online textbook for a group of students in her online class (Condition 1) to the recommended weekly minutes of reading (Condition 2). If the instructor wants to see if her online students are reading significantly less than the recommended times, then the appropriate one-tailed null hypothesis is: a. μ1 < μ2 b. μ1 ≥ μ2 c. μ1 ≄ μ2 d. μ1 > μ2 e. μ1 ≤ μ2

μ1 ≥ μ2