Which of the following statements are true? The pooled-variances t-test is used whenever the population standard deviations are assumed to be equal regardless of the sample size. The unequal-variances t-test is used whenever the population standard deviations are unknown and cannot be assumed to be equal. The z-test can be used as a close approximation to the unequal-variances t-test when the population standard deviations are not assumed to be equal, but samples are large (each n 30). All of these statements are true. None of these statements is true
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Which of the following statements are true?
-
The pooled-variances t-test is used whenever the population standard deviations are assumed to be equal regardless of the
sample size . -
The unequal-variances t-test is used whenever the population standard deviations are unknown and cannot be assumed to be equal.
-
The z-test can be used as a close approximation to the unequal-variances t-test when the population standard deviations are not assumed to be equal, but samples are large (each n 30).
-
All of these statements are true.
-
None of these statements is true.
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- 3. Which of the following are practical ways to assess equal variances of the residuals? Select all that apply a. Hartley's F-max test (provided data look normal and sample sizes are same); b. Bartlett's test (provided normality seems to hold; sample sizes do not have to be the same); c. Levene's test (normality and equal sample sizes aren't needed) d. Boxplots of residuals, or boxplots of standardized residuals, or boxplots of the original data. e. Boxplots of cats and dogs.Which is not one of the major assumptions typically associated with parametric tests of significance? A. Random Selection B. Homogeneity of Variance C. Absence of restricted rangesA supplier of digital memory cards claims that no more than 1% of the cards are defective. In a random sample of 600 memory cards, it is found that 3% are defective, but the supplier claims that this is only a sample fluctuation. How many populations? 01 What is the parameter? O tandard Deviation Variance Difference between Means Proportion Mean
- Suppose that we are interested in comparing the academic success of college students who belong to fraternal organizations and the academic success of those who do not belong to fraternal organizations. Random samples of size 40 are taken from each population where the variances and standard deviations are known. Sample Size Mean GPA Variance (2) 2.03 2.21 Fraternity member (f): 40 Nonmembers (n): 40 .46 .35 Construct a 96% confidence interval estimate for the difference between the mean GPAS (uf- un). Interpret this interval estimate. What can you conclude about the mean GPAs of the two groups?One-Way Airfares The average one-way airfare from Pittsburgh to Washington D.C. is $236. A random sample of 19 one-way fares during a particular month had a mean of $208 with a standard deviation of $43. At α=0.05, is there sufficient evidence to conclude a difference from the stated mean?Which samples show unequal variances? Use a = .10 in all tests. Show the critical values and degrees of freedom clearly and illustrate the decision rule. s1 = 10.2, n1 = 22, s2 = 6.4, n2 = 16, two-tailed test s1 = .89, n1 = 25, s2 = .67, n2 = 18, right tailed test s1 = 124, n1 = 12, s2 = 260, n2 = 10, left-tailed test
- Violation of which assumption below for the two-factor ANVOA is not a cause for concern with large sample sizes? a. The populations from which the samples are selected must have equal variances. b. The populations from which the samples are selected must be normal. c. A violation of any assumption below would be a concern, even with large sample sizes. d. The observations within each sample must be independent.One of the following is an example of a question that might be asked to ascertain a problem with a nonrepresentative sample. Which one? O Do the signs of the residuals alternate? O Does the population have an omitted variable? O Do the residuals show nonconstant variance? O Does the sample contain about the same geographic coverage as the population?A study was done using a treatment group and a placebo group. The results are shown in the table. Assume that the two samples are independent simple random. samples selected from normally distributed populations, and do not assume that the population standard deviations are equal. Complete parts (a) and (b) below. Use a 0.01 significance level for both parts. a. Test the claim that the two samples are from populations with the same mean. What are the null and alternative hypotheses? OA. Ho: H1 H2 H₁₁₂ The test statistic, t, is (Round to two decimal places as needed.) OB. Ho: H₁₂ H₁: H₁Which of the following is NOT true when using one-way analysis of variance for testing equality of three or more population means? ..... Choose the correct answer below. A. Small P-values indicate that the decision is to reject the null hypothesis of equal means. B. The numerator of the F test statistic measures variation between sample means. C. The conclusion that there is sufficient evidence to reject the claim of equal population means does not indicate a particular mean is different from the others. O D. Small F test statistics indicate that the decision is to reject the null hypothesis of equal means.A study was done using a treatment group and a placebo group. The results are shown in the table. Assume that the two samples are independent simple random H samples selected from normally distributed populations, and do not assume that the population standard deviations are equal. Complete parts (a) and (b) below. Use a 0.01 significance level for both parts. a. Test the claim that the two samples are from populations with the same mean. What are the null and alternative hypotheses? OA. Ho: #₁ = 1₂ H₁: H₁ H₂ OC. Ho: H₁You wish to test the following claim (��) at a significance level of �=0.002. ��:�1=�2 ��:�1≠�2You believe both populations are normally distributed, but you do not know the standard deviations for either. However, you also have no reason to believe the variances of the two populations are not equal. You obtain the following two samples of data. Sample #1 Sample #2 50.2 77.2 87.1 65 64.2 58.4 78 60.5 72.6 53.1 51.2 75.6 64.2 93.6 68.6 63.8 71.9 74.9 74.5 54.6 59.2 61.8 90.1 73.6 55.4 62.6 68.6 71.6 67.9 87.3 51.9 85.2 81.3 76.3 54 59.6 59.6 88.6 50.8 What is the test statistic for this sample? (Report answer accurate to three decimal places.)test statistic = What is the p-value for this sample? For this calculation, use the degrees of freedom reported from the technology you are using. (Report answer accurate to four decimal places.)p-value =SEE MORE QUESTIONSRecommended textbooks for youMATLAB: An Introduction with ApplicationsStatisticsISBN:9781119256830Author:Amos GilatPublisher:John Wiley & Sons Inc
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