Exam 12: Simple Regression

In a sample of size n = 23, a sample correlation of r = .400 provides sufficient evidence to conclude that the population correlation coefficient exceeds zero in a right-tailed test at:

To calculate a residual for the ith observation, we do not need the:

A hypothesis test is conducted at the 5 percent level of significance to test whether the population correlation is zero. If the sample consists of 25 observations and the correlation coefficient is 0.60, then the computed test statistic would be:

If r = .55 and n = 16, then the correlation is significant at α = .05 in a two-tailed test.

Which is not an assumed property of the errors in a population regression model?

If the fitted regression is Y = 3.5 + 2.1X (R² = .25, n = 25), it is incorrect to conclude that:

A fitted regression Profit = -570 + 30 Sales (all variables in thousands of dollars) was estimated from a random sample of pharmacies. From this regression, in order to break even (Profit ≥ 0), a pharmacy's Sales would have to be at least:

In a sample of n = 40, a sample correlation of r = .400 provides sufficient evidence to conclude that the population correlation coefficient exceeds zero in a right-tailed test at:

In a sample of n = 36, the critical value of Student's t for a two-tailed test of significance of the slope for a simple regression at α = .05 is:

A researcher's Excel results are shown below using Femlab (labor force participation rate among females) to try to predict Cancer (death rate per 100,000 population due to cancer) in the 50 U.S. states. Regression Statistics Multiple R 0.313422848 R Square 0.098233882 Adjusted R Square 0.079447088 Standard Error 32.07003698 Observations 50 Variable Coefficients Standard Error t Stat Intercept 343.619889 61.0823514 5.62552 Femlab -2.2833659 0.99855319 -2.28667 Which of the following statements is not true?

For a regression with 200 observations, we expect that about 10 residuals will exceed two standard errors.

The variable used to predict another variable is called the:

Amelia used a random sample of 100 accounts receivable to estimate the relationship between Days (number of days from billing to receipt of payment) and Size (size of balance due in dollars). Her estimated regression equation was Days = 22 + 0.0047 Size with a correlation coefficient of .300. From this information we can conclude that:

In a sample of n = 20, the critical value of the correlation coefficient for a two-tailed test at α = .05 is:

In a sample of n = 20, the Student's t test statistic for a correlation of r = .400 would be:

A fitted regression for an exam in Prof. Hardtack's class showed Score = 20 + 7 Study, where Score is the student's exam score and Study is the student's study hours. The regression yielded R² = 0.50 and SE = 8. Bob studied 9 hours. The quick 95 percent prediction interval for Bob's grade is approximately:

In a sample of n = 27, the critical value of Student's t for a two-tailed test of significance for a simple bivariate regression at α = .05 is:

A prediction interval for Y is widest when X is near its mean.

A different confidence interval exists for the mean value of Y for each different value of X.

If the residuals violate the assumption of normality, we expect that: