Suppose that you sample two normal populations inde- pendently. The variances of these two populations are oj and ož. You take random samples of sizes n, and n and observe sample variances of sĩ and sz. a. If n¡ = n2 = 21, how large must the fraction s1/s2 be before you can reject the null hypothesis that of is no greater than ơž at the 5% significance level? b. Answer part a when n¡ = n, = 41. c. If s¡ is 25% greater than s2, approximately how large must n¡ and n, be if you are able to reject the null hypothesis in part a at the 5% significance level? Assume that n¡ and nɔ are equal.

A high school conducts a dependent sample experiment to test if there is a difference between the number of times students are absent in the fall and winter months. You have data for the following 5 students: STUDENT FALL WINTER 1 2 3 4 5 2 0 1 2 O What do you conclude about this school's absences? (Assume standard a = 0.05) 2 1 2 4 T O There is no difference between the Fall and Winter months. O There is a statistically significant difference between the Fall and Winter months. There is a difference but it is only somewhat statistically significant. There is not enough data to determine if there is a difference in absences.

7

In case of hypothesis testing in places where population variances are unknown and sample size is large (nl and n22 30), sample variances can be a good approximation of population variances. Which best describe this statement? Select one: O a. None of the choices O b. The statement is true c. The statement is false O d. Not enough data to support the statement O e. The statement is neither true nor false

You have a population mean µ=27, and a sample mean of 29. The sample variance equals 6. Compute Cohen’s d

If s = 15 and the estimated standard error is 5, then the sample size must be equal to ______.

The mean height of 15-year-old boys (in em) is 175 and the variance is 64. For girls, the mean is 165 and the variance is 64. Assuming that the two populations are nomally distributed. If eight boys and eight girls were sampled, then the probability that the mean height of the sample of boys would be higher than the mean height of the sample of girls 18: O 0 9878 O 0.0062 O 0.9938 0 9972 Let E[X(Y-1)] 10, E[X(Y#1)] 20, V(X) Then E(Y) 8. V(Y) 12 and V(X+Y) 30. O 14/5 12/5 2

hey how would i do this?

Sample A Sample B s2 22 25 n 10 8 We want to test the hypothesis that population B has a smaller variance than population A.

Which of the following is not a sample property of OLS?   a. Sample covariance of  each included variable and the residuals is zero   b. the sum of all residuals is zero   c. the average of all residuals is zero   d. the covariance of x and y is on the regression line.