Question

A random sample of 99 light bulbs had a mean life of x = 415 hours with a standard deviation of a = 34 hours. Construct a 90% confidence interval for the mean life, μ, of all light bulbs of this type. Round to the nearest ones place?

Answer 1

solution Given that c = 90% - X = 415 S = 34 n - 99 A 90% confidence interval t is, df = n-1= 99-1 -98 x = 1 c = 1-0.90 = 0.1 = 0.1 = 0.05 ole 2 pole of df = 0.05,98 = 1.661 Margin of eerot & a y, df (mm) = 1.661 (rag - 5.6 The 90% confidence interval mean is, - BE 415-516 2 415 +5.6 1 (409, 4, 420.6)