Statistics Chapter 8
Which of the following explains why point estimation can be a useful procedure to estimate a population mean? It defines the range of scores within which the population mean is likely to be contained. The sample mean is equal to the population mean on average. The sample mean is an unbiased estimator of the population mean. both B and C
both B and C
Which measure of effect size is most commonly reported with a t test? eta-squared omega-squared t statistic Cohen's d
Cohen's d
A researcher conducts two t tests. Test 1 is a two-tailed test with a smaller sample size at a .05 level of significance. Test 2 is a two-tailed test with a larger sample size at a .05 level of significance. What do you know about the degrees of freedom for each test? Test 1 is associated with larger degrees of freedom. Test 2 is associated with larger degrees of freedom. Each test is associated with the same degrees of freedom. It depends; there is not enough information to answer this question.
Test 2 is associated with larger degrees of freedom.
State the critical value(s) for the following two-tailed t test at a .05 level of significance: t(∞). ±1.645 ±1.96 the same as for a two-tailed z test at a .05 level of significance both B and C
both B and C
A key difference between a t statistic and a z statistic is that the standard error is ________ to compute a t statistic. removed replaced estimated placed in the numerator
estimated
The ________ is an inferential statistic used to determine the number of standard deviations in a t distribution that a sample mean deviates from the mean value or mean difference stated in the null hypothesis. t distribution t statistic standard error degrees of freedom
t statistic
Which of the following summarizes a t test that was significant and associated with a large effect size? t(22) = 3.02, p < .05, d = .36 t(30) = 1.03, p > .05, d = .20 t(60) = 1.76, p > .05, d = .45 t(12) = 2.95, p < .05, d = .82
t(12) = 2.95, p < .05, d = .82
Which of the following best describes the goal of estimation? to determine the extent to which a result is significant to estimate the significance of a result to narrow in on the true population mean by defining limits within which it is likely to be contained both A and B
to narrow in on the true population mean by defining limits within which it is likely to be contained
State the critical value(s) for a t test using a .05 level of significance in the lower tail only: t(24). ±1.711 -1.711 ±2.064 -2.064
-1.711
As a requirement for the t test, researchers compute any type of t test with samples selected from populations in which the population variance is known the population size is very large the population variance is unknown the population is the same size as the sample
the population variance is unknown
In a sample of 20 participants, a researcher estimates the 95% CI for a sample with a mean of M = 5.4 and an estimated standard error (SM) of 1.6. What is the lower confidence limit for this interval? 2.1 3.8 7.0 8.8
2.1
A researcher reports with 90% confidence that 31% to 37% of Americans believe in ghosts. What is the point estimate for this interval? 31% 34% 37% 31% to 37%
34%
In a sample of 20 participants, a researcher estimates the 95% CI for a sample with a mean of M = 5.4 and an estimated standard error (SM) of 1.6. What is the upper confidence limit for this interval? 2.1 3.8 7.0 8.8
8.8
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? 80% CI 12.1, 32.5 80% CI 17.6, 27.0 80% CI 15.9, 28.7 There is not enough information to answer this question.
80% CI 15.9, 28.7
In a sample of 28 participants, a researcher estimates the 95% CI for a sample with a mean of M = 1.5 and an estimated standard error (SM) of 0.3. What is the confidence interval at this level of confidence? 95% CI 1.0, 2.0 95% CI 1.2, 1.8 95% CI 0.9, 2.1 There is not enough information to answer this question.
95% CI 0.9, 2.1
It is most appropriate to report effect size with a significant result. Why is it generally inappropriate to report effect size with insignificant results? Because insignificant results will always have an effect size equal to 0. Because insignificant results indicate that an effect size is also insignificant. Because it makes little sense to report the size of an effect that you just concluded doesn't exist. Because the probability of the size of an effect varies depending on the significance of the result.
Because it makes little sense to report the size of an effect that you just concluded doesn't exist.
Is a one-sample t test reported differently for one-tailed and two-tailed tests? No, the same values are reported. It depends on whether the results were significant. Yes, only significant results for a two-tailed test are reported. It can be reported differently when the effect size is large.
No, the same values are reported.
A researcher conducts a study and concludes that a new behavioral health treatment program significantly reduces one's risk for disease compared with risk levels in the general population (d = -0.64). Interpret the size of this effect. 64% of the variability in risk level can be accounted for by the new treatment. 64% of the new treatment can be accounted for by the risk levels. Risk levels in the population shifted 0.64 standard deviations below the mean. Risk levels in the population shifted 0.64 standard deviations above the mean.
Risk levels in the population shifted 0.64 standard deviations below the mean.
A researcher conducts two t tests. Test 1 is a one-tailed test with a smaller sample size at a .05 level of significance. Test 2 is a one-tailed test with a larger sample size at a .05 level of significance. What do you know about the critical values for each test? Test 1 is associated with smaller critical values. Test 2 is associated with smaller critical values. Each test is associated with the same critical values. It depends; there is not enough information to answer this question.
Test 2 is associated with smaller critical values.
A researcher reports that college students consume an average of 3.6 alcoholic drinks per week. What is the interval estimate in this example? 3.6 The interval estimate is not given.
The interval estimate is not given.
The mean crying time of infants during naptime at a local preschool is 12 minutes. The school implements a new naptime routine in a sample of 25 infants and records an average crying time of 8±4.6 (M±SD) minutes. Test whether this new naptime routine reduced crying time at a .05 level of significance. The new naptime routine significantly reduced crying time, t(24) = -4.35, p < .05. The new naptime routine did not reduce crying time, t(24) = -4.35, p < .05. The new naptime routine did not reduce crying time, t(24) = 0.92, p > .05. The new naptime routine significantly reduce crying time, t(24) = 0.92, p < .05.
The new naptime routine significantly reduced crying time, t(24) = -4.35, p < .05.
A local elementary school determined that the average number of volunteers for their "Step into Spring" annual fundraiser has been 14 persons on average (per event). After taking additional measures to recruit volunteers this year, they got 28 people to volunteer. Test whether these additional measures increased the number of volunteers at a .05 level of significance. Yes, because the number of volunteers doubled; this is a significant increase. No, this is not a significant increase because the error term is too large. This would have been significant if it were a two-tailed test. There is not enough information to answer this question.
There is not enough information to answer this question.
A researcher selects a sample of 16 women and asks them to rate how important a sense of humor is in someone they want a long-term relationship with. She records scores averaging 1.6±0.8 (M±SD) on a rating scale from -3 (not important at all) to +3 (very important). Assuming that an average score of 0 is the null hypothesis, test whether or not women find this trait important at a .05 level of significance. Women found this trait to be important, and this result was significant, t(16) = 8.00, p < .05. Women found this trait to be important, and this result was significant, t(15) = 8.00, p < .05. Women did not find this trait to be important, p > .05. There is not enough information to answer this question.
Women found this trait to be important, and this result was significant, t(15) = 8.00, p < .05.
A point estimate is typically reported with an interval estimate. Why? Using only a point estimate is associated with low certainty. The interval estimate gives researchers a higher level of confidence. The interval estimate adds certainty to the estimate of the population mean. all of the above
all of the above
Computing a one-sample t test is appropriate when participants are assigned to only one group the population variance is unknown participants are observed one time all of the above
all of the above
The t distribution is similar to the z distribution except it is associated with greater variability it is characterized by "thicker" tails compared with the z distribution it is associated with scores being more likely in the tails of the distribution all of the above
all of the above
Which of the following is an assumption for computing any type of independent sample t test? Data in the population being sampled are normally distributed. Data were obtained from a sample that was selected using a random sampling procedure. The probabilities of each measured outcome in a study are independent. all of the above
all of the above
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? d = 0.33; small effect size d = 0.33; medium effect size d = 3.00; large effect size There is not enough information to answer this question.
d = 0.33; medium effect size
Which type of error is used to compute the confidence interval for one sample selected from a population with an unknown variance? standard error estimated standard error estimated standard error for the difference estimated standard error for the difference scores
estimated standard error
A statistical procedure in which a sample statistic is used to estimate the value of an unknown population parameter is called an educated guess appropriation estimation significance testing
estimation
A researcher conducts a study measuring comparing the obesity rate in a small community to the known obesity rate in the United States. Assuming that the population variance in unknown, what type of t test is appropriate for this study? one-sample t test two-independent sample t test not enough information
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? one-sample t test two-independent sample t test There is not enough information to answer this question.
one-sample t test
You read about a study testing whether night shift workers sleep the recommended 8 hours per day. Assuming that the population variance of sleep (per day) is unknown, what type of t test is appropriate for this study? one-sample t test two-independent sample t test There is not enough information to answer this question.
one-sample t test
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 one-sample t test two-independent sample t test There is not enough information to answer this question.
two-independent sample t test
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? The estimated standard error must be known. The population variance must be known. The sample size must be known. The sample mean and sample variance must be known.
The population variance must be known.
State the critical value(s) for a t test using a two-tailed test at a .05 level of significance: t(20). ±1.725 ±2.093 ±2.086 ±0.687
±2.086
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? 32 30 31 There is not enough information to answer this question.
31
Two researchers (A and B) compute a one-sample t test. For both tests, the mean difference between the sample and value stated in the null hypothesis is 5, but the standard error is smaller for Researcher A. Which test is more likely to result in a decision to reject the null hypothesis? Researcher A. Researcher B. The likelihood is the same for both researchers. There is not enough information to answer this question.
Researcher A.
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? Researcher A. Researcher B. The likelihood is the same for both researchers. There is not enough information to answer this question.
Researcher B.
The average response time to a bank robbery is about 9 minutes. A local community wants to improve on this time, so they implement advanced training seminars. They find that the new response time for a sample of 36 police officers is 8±4.2 (M±SD) minutes. Test whether this advanced training seminar reduced response time at a .05 level of significance. This advanced training seminar significantly reduced response time, t(35) = 11.43, p < .05. This advanced training seminar significantly reduced response time, t(35) = -1.43, p < .05. This advanced training seminar did not reduce response time, t(35) = -1.43, p > .05 There is not enough information to answer this question.
This advanced training seminar did not reduce response time, t(35) = -1.43, p > .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? One-tailed test because the p value is equal to .05 Two-tailed test because the p value is equal to .05 It could be a one-or a two-tailed test
Two-tailed test because the p value is equal to .05
A researcher reports that the mean time it takes to complete an experimental task is 1.4±8.0 (M±SD) seconds. 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? d = 0.05; small effect size d = 0.50; medium effect size d = 1.05; large effect size There is not enough information to answer this question.
d = 0.05; small effect size
A researcher reports a significant effect in some population. If he computes both an eta-squared and an omega-squared effect size estimate, then which estimate will be the largest? eta-squared omega-squared It depends on the sample size. It depends on the value of the t statistic.
eta-squared
A researcher reports a significant effect with t(14) = 3.24. Compute eta-squared for this result. n2 = 0.43 (large effect size) n2 = 0.43 (medium effect size) ω2 = 0.37 (large effect size) ω2 = 0.37 (medium effect size)
n2 = 0.43 (large effect size)
The estimated standard error in the t statistic uses the ________ to estimate the ________ when the population variance is unknown. sample variance; population variance population variance; sample variance standard error; sample variance degrees of freedom; sample size
sample variance; population variance
