psych stat exam 3
A researcher compares the height of male executives in the U.S. to the average height of males (µ = 67 inches). He determines that the average height of male executives is 70 inches (95% confidence interval [CI] 68-72). Based on this result, what would the decision have been for a hypothesis test? a. reject the null b. retain the null c. there is not enough information
A
To compute a one-sample t test, a researcher has to know many values. Which of the following is NOT a value that the researcher must know to compute this test? a. estimated standard error b. population variance c. sample size d. sample mean and sample variance
B
All other things being equal, reducing the level of significance from .05 to .01 will ________ the value of the test statistic for a related samples t test. a. increase b. decrease c. have no effect on
C
For the related samples t test, assuming that all other values remain constant, then as samples size increases, a. the value of the test statistic increases b. the power to detect an effect increases the estimate for standard error decreases d. all of the above
D
The confidence interval for samples selected from a population with an unknown variance is computed using critical values from the t table. This is true for which of the following types of samples? a. one-sample b.two-independent sample c. related samples d. all of the above
D
A two-independent sample t test is used when the same participants are observed in each of two groups. TRue/False
False
State the critical value(s) for a t test using a two-tailed test at a .05 level of significance: t(20). a. +-2.086 b.+-1.725 c.+-2.093 d. +-0.687
a
One difference between a repeated measures design and a matched samples design is that a.only one design is a type of related sample design b.only one design increases the power to observe an effect c. only one design involves observing the same participants in each group d,only one design eliminates between-persons variability
c
A study in which 26 participants are observed two times is associated with 26 degrees of freedom for a related samples t test. true/false
false
As the value of the test statistic for a related samples t test increases, the likelihood of deciding to retain the null hypothesis also increases. true/false
false
If d = 0.28, then we conclude that mean scores in some population have shifted 0.28 standard deviations below the mean. true/false
false
When the null hypothesis is outside a confidence interval, this indicates that it would likely be retained with hypothesis testing. true/false
false
The estimated standard error is used in the formula to estimate the population mean for the one-sample t. true/false
true
In a sample of 12 participants, a researcher estimates the 80% CI for a sample with a mean of M = 22.3 and an estimated standard error (SM) of 4.7. What is the confidence interval at this level of confidence? a. 80% CI 12.1, 32.5 b. 80% CI 17.6, 27.0 c. 80% CI 15.9, 28.7 d. there is not enough information
A
A researcher estimates the 95% CI for a sample with a mean of M = 3.26 and a standard error (σM) of 0.91. What is the upper confidence limit for this interval? a. 1.48 b. 2.35 c. 4.17 d. 5.04
B
To increase the value of estimated Cohen's d, a researcher increases the sample size. Will this change the value of d? a. No; the sample size is not used to compute effect size. b. No; as sample size increases, effect size decreases. c. Yes; as sample size increases, effect size decreases. d. Yes; as sample size increases, effect size increases.
A
A researcher records the time it takes (in seconds) for participants to respond (by pressing a key) to a familiar versus an unfamiliar word flashed onto a computer screen. In this study, the difference in response time for each participant is compared. The type of design described here is called a a. repeated measures design b. matched samples design c. both A and B
A
In a sample of 18 participants, a researcher estimates the 80% CI for a sample with a mean of M1-M2 = 8.8 and an estimated standard error for the difference (SM1-M2) of 1.8. What is the lower confidence limit for this interval? a. 6.4 b. 7.0 c. 10.6 d. 11.2
A
In a sample of 26 participants, a researcher estimates the 90% CI for a sample with a mean of MD= 0.6 and an estimated standard error for the difference scores (SMD) of 0.1. What is the upper confidence limit for this interval? a. .77 b. -0.5 c. 1.7 d. 2.5
A
Is a one-sample t test reported differently for one-tailed and two-tailed tests? a. No, the same values are reported. b. It depends on whether the results were significant. c. Yes, only significant results for a two-tailed test are reported. d. It can be reported differently when the effect size is large.
A
A researcher finds that the mean difference in productivity between employees working the morning shift (n = 16) and the night shift (n = 10) is 5.0 units, and the estimated standard error for the difference is 2.7 units. If the null hypothesis states that there is no difference in productivity, then is this result significant at a .05 level of significance? a. yes this result is significant b. no this result is not significant c. there is not enough information to answer this question
B
A researcher increases his level of confidence from 90% to 95%. What will happen to the precision of his estimate? a. The estimate will be more precise. b. The estimate will be less precise. c. The precision of his estimate will not change. d. It depends on the size of the population.
B
A researcher reports that mean ratings of liking for some food are 0.8±2.4 (M±SD). If the null hypothesis was that the mean equals 0, then what is the effect size for this test using estimated Cohen's d? a. d = 0.33; small effect size b. d = 0.33; medium effect size c. d = 3.00; large effect size d. There is not enough information to answer this question.
B
A researcher conducts a study in which the same participants are observed across each level of the independent variable. If there are only two levels of the independent variable, then what type of t test is appropriate for this study? a. one-sample t test b. two-independent sample t test c.related samples t test d.There is not enough information to answer this question.
C
A researcher records the level of attention among 18 students during an interactive and lecture portion of a single class. If she computes a related samples t test at a .05 level of significance (two-tailed test), then what is the critical value for this test? a. ±1.734 b. ±1.740 c. ±2.110 d. ±2.101
C
Compared to the two-independent sample t test, the related samples design decreases a. power b.effect size c. standard error d. significance
C
Which of the following is a characteristic of confidence intervals? a. The less certain an estimate, the more precise the estimate. b.The more certain an estimate, the less precise the estimate. c. both a and b
C
The t distribution is similar to the z distribution except a. it is associated with greater variability b. it is characterized by "thicker" tails compared with the z distribution c.it is associated with scores being more likely in the tails of the distribution d. all of the above
D
Which of the following is an assumption for the two-independent sample t test, but not the one-sample t test? a. normality b. random sampling c. independednce d. equa variance
D
A professor compares final exam scores in his psychology class to final exam grades in another comparable professor's class. Assuming that the population variance of exam scores is unknown, what type of t test is appropriate for analyzing differences between these classes? a. one-sample t test b. two-independednt sample t test c. there is not enough information to answer this question
B
