Question:Chapter 6, Section 4-D, Exercise 180

Use the formula to find the standard error of the distribution of differences in sample means,x1-x2.

Samples of size120from Population1with mean90and standard deviation14and samples of size90from Population2with mean79and standard deviation15

Round your answer for the standard error to two decimal places.

standard error=Enter your answer in accordance to the question statement

the absolute tolerance is +/-0.01

Chapter 6, Section 4-D, Exercise 184

Use at-distribution to answer this question. Assume the samples are random samples from distributions that are reasonably normally distributed, and that at-statistic will be used for inference about the difference in sample means. State the degrees of freedom used.

Find the endpoints of thet-distribution with2.5%beyond them in each tail if the samples have sizesn1=17andn2=21.

Enter the exact answer for the degrees of freedom and round your answer for the endpoints to two decimal places.

degrees of freedom=

endpoints=

Chapter 6, Section 4-D, Exercise 186

Use at-distribution to answer this question. Assume the samples are random samples from distributions that are reasonably normally distributed, and that at-statistic will be used for inference about the difference in sample means. State the degrees of freedom used.

Find the proportion in at-distribution less than-1.4if the samples have sizesn1=30andn2=40.

Enter the exact answer for the degrees of freedom and round your answer for the area to three decimal places.

degrees of freedom=

proportion=