distribution. You will only receive credit for the original exam With g opothesi

Question

distribution. You will only receive credit for the original exam With g opothesis testing, you must follow each of the steps in the guidelines for hypothesis testing in the textbook. Number each of the steps from 394. You may use Mathematica , Maple or Excel unless otherwise specified. 9 Q64 Sample size for mean (calculator life) a. A researcher wants to estimate the average life of a calculator to within 0.75 years of the true value. Past experience indicates that the standard deviation is 3.4 years. How large a sample must she select if she wants her answer to be within 0.75 years with a 95% level of confidencee? 4 points e a sample must she select if she wants her answer to be within 0.7 years with a 99% level of confidencee? 4 points

Explanation / Answer

Question 9

Part a

We are given

E = 0.75

= 3.4

C = 95%

Z = 1.96 (by using z-table)

n = (Z*/E)^2 = (1.96*3.4/0.75)^2 = 78.94915

Required sample size = 79

Part b

We are given

E = 0.7

= 3.4

C = 99%

Z = 2.5758 (by using z-table)

n = (Z*/E)^2 =(2.5758*3.4/0.7)^2 = 156.5258

Required sample size = 157

Question 10

We are given

Xbar = 2

S = 0.17

n = 23

df = n – 1 = 23 – 1 = 22

C = 95% = 0.95

Critical t value = 2.0739

Confidence interval = Xbar -/+ t*S/sqrt(n)

Confidence interval = 2 -/+ 2.0739*0.17/sqrt(23)

Confidence interval = 2 -/+ 2.0739* 0.03544745

Confidence interval = 2 -/+ 0.0735

Lower limit = 2 - 0.0735 = 1.9265

Upper limit = 2 + 0.0735 = 2.0735

Confidence interval = (1.9265, 2.0735)

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