Question

3 5 Incorrect Your answer is incorrect . Your lower confidence limit is not correct • Your upper confidence limit is not correct. The scores on an examination in psychology are approximately normally distributed with mean 500 and an unknown standard deviation. The following is a random sample of scores from this examination. 410, 438, 469, 501, 527, 539,586 Find a 90% confidence interval for the population standard deviation. Then complete the table below. Carry your intermediate computations to at least three decimal places. Round your answers to at least two decimal place 36:49 What is the lower limit of the 90% confidence interval? What is the upper limit of the 90% confidence interval? 124.74 Х 5

Answer 1

A B с D E F 1 410 2 variance 3737.2381 VAR.S(A1:A7 438 469 3 4 501 5 527 6 539 7 586

3737.2381 Na 7 The critical values for a = 0.1 and df = 6 degrees of freedom are xỉ = xỉ_0/2.1–1 = 1.6354 and xi = x2,1-1 = 12.5916. The corresponding confidence interval is computed as shown below: CI(Variance) (n-1)s (n-1) s xỉ 2,1-1 1-a 2,n-1 (7-1) x 3737.2381 (7-1) x 3737.2381 12.5916 1.6354 (1780.8262, 13711.4242) Now that we have the limits for the confidence interval, the limits for the 90% confidence interval for the population standard deviation are obtained by simply taking the squared root of the limits of the confidence interval for the variance, so then: CI(Standard Deviation) 1780.8262, 13711.4242 (42.1998, 117.0958)