1. If an economist wishes to determine whether there is evidence that average family income in a community exceeds $25,000. The best null hypothesis is:
a) μ ≤ 25,000.
b) μ = 25,000.
c) μ > 25,000.
d) μ ≥ 25,000.
2. The manager of an online shop wants to determine whether the mean length of calling time of its customers is significantly more than 3 minutes. A random sample of 100 customers was taken. The average length of calling time in the sample was 3.1 minutes with a standard deviation of 0.5 minutes. At a 0.05 level of significance, it can be concluded that the mean of the population is
a) significantly not different from 3.10.
b) not significantly greater than 3.
c) significantly less than 3.
d) significantly greater than 3.
3. Which of the following is the correct the null and alternative hypotheses to determine if the average SSATL score of Japanese managers differs from the average SSATL score of American managers?
a) H0: MA - MJ = 0 versus Ha : MA - MJ ≠ 0
b) H0: XA - XJ = 0 versus Ha : XA -XJ ≠ 0
c) H0:MA - MJ ≥ 0 versus Ha : MA - MJ
d) H0: MA - MJ ≤ 0 versus Ha : MA - MJ > 0
4. Assume that you are testing the difference in the means of two independent populations at the 0.05 level of significance. The null hypothesis is: Ho : MA - MB ≥ 0 and you have found the test statistic is z = -1.92. What should you conclude?
a) The mean of pop. A is greater than the mean of pop. B because p > α.
b) The mean of pop. B is greater than the mean of pop. A because p
c) The mean of pop. A is greater than the mean of pop. B because p
d) There is no significant difference in the two means because p > α.
5. Under what conditions can the t-distribution be correctly employed to test the difference between two population means?
a) When the samples from the two populations are small and the population variances are unknown
b) When the population variances are assumed to be equal
c) All of the above.
d) When the two populations of interest are assumed to be normally distributed
6. A hypothesis test for the difference between two means is considered a two-tailed test when:
a) the standard deviations are unknown.
b) the alpha level is 0.10 or higher.
c) the null hypothesis states that the population means are equal.
d) the population variances are equal.
7. A fast food chain operation is interested in determining whether the mean per customer purchase differs by day of the week. To test this, it has selected random samples of customers for each day of the week. Based on ANOVA, F test statistic of 1.18, p-value is 0.32, and F critical value is 2.24. What conclusion can we make?
a) There is no basis for concluding that mean sales is different for the different days of the week.
b) Based on the p-value, the null hypothesis should be rejected since the p-value exceeds the alpha level.
c) The experiment is conducted as an imbalanced design.
d) Based on the critical value, the null should be rejected
8. If a pair of variables have a strong curvilinear relationship, which of the following is true?
a) The correlation coefficient will be able to indicate that curvature is present.
b) The correlation coefficient will be equal to zero.
c) A scatter plot will not be needed to indicate that curvature is present.
d) The correlation coefficient will not be able to indicate the relationship is curved.
9. Which of the following statements is true with respect to a simple linear regression model?
a) All of the above are true.
b) If the correlation coefficient between the x and y variables is negative, the sign on the regression slope coefficient will also be negative.
c) If the correlation between the dependent and the independent variable is determined to be significant, the regression model for y given x will also be significant.
d) The percent of variation in the dependent variable that is explained by the regression model is equal to the square of the correlation coefficient between the x and y variables.
10. If Regression analysis results show R-square is 0.7835, and correlation coefficient is 0.8851, which of the following is true?
a) linear association between x and y explains about 78.4 percent of the variation in y.
b) x explains about 88.5 percent of the variation in y.
c) y explains about 88.5 percent of the variation in x.
d) y explains about 78.4 percent of the variation in x.
11. In a regression analysis situation, the standard error of the slope is:
a) equal to the square root of the standard error of the estimate.
b) a measure of the variation in the regression slope from sample to sample.
c) a measure of the amount of change in y that will occur for a one-unit change in x.
d) All of the above.
12. Assume that you have calculated a prediction of y-estimate = 110 where the specific value for x is equal to the average value of x. Also assume that n = 201 and that the standard error of the estimate is sε = 4.5. Find the approximate 95 percent prediction interval.
a) About 98.4 ----- 121.6
b) About 101 ----- 119
c) About 105.5 ----- 104.5
d) About 109.4 ----- 110.6
13. Which of the following is a correct interpretation for the regression slope coefficient?
a) The average change in x of a one-unit change in y will be b1 units.
b) The average change in y of a one-unit change in x will be b1 units.
c) For each unit change in x, the dependent variable will change by b1 units.
d) For a one-unit change in y, we can expect the value of the independent variable to change by b1 units on average.
14. Which of the following statements is true?
a) The y-intercept will usually be negative in a multiple regression model when the regression slope coefficients are predominately positive.
b) None of the above
c) If the confidence interval estimate for the regression slope coefficient, based on the sample information, crosses over zero, the true population regression slope coefficient could be zero.
d) R-square will tend to be smaller than the adjusted R-squared values when insignificant independent variables are included in the model.