If 45 officials in student services earned an average of x(with a line over it) = $50,340 each year:

a. Assume that the standard deviationis 16,920 for salaries of officials. Find the 90% confidence intervalfor the population meansalary of such personal. What is the margin of error.

b. If SD is 10,780, Find the 90% confidence interval and margin of error?

c.If SD is 4830.00, find the 90% confidence interval and margin of error?

d. Compare the lengths of confidence intervalsin a-c, As the sd decreases does the length of the 90%

confidence level decrease?

e. Compare the lengths of the confidence interval for parts (a) through (c). As the SD decreases, does the length of a 90% confidence interval decrease?

(Please see the attached file)

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