Question

Construct the indicated confidence interval for the difference between the two population means. Assume that the two samples are independent simple random samples selected from normally distributed populations. Do not assume that the population standard deviations are equal. A paint manufacturer wished to compare the drying times of two different types of paint. Independent simple random samples of 11 cans of type A and 9 cans of type B were selected and applied to similar surfaces. The drying times, in hours, were recorded. The summary statistics are as follows. Type A x1 = 75.7 hrs s1 = 4.5 hrs n1 = 11 Type B x2 = 64.3 hrs s2 = 5.1 hrs n2 = 9 Construct a 98% confidence interval for p 1 - u2, the difference between the mean drying time for paint of type A and the mean drying time for paint of type B.

Answer 1

Independent simple random Population standard deviations a FT Samples not equal ave А- В 757 ha 64.3 has Sisus his ne au s=5. I ho 12=9 confidence Interval for Me-Ma x=002 df = nitha all +9-2 = 18 df =18 a=0.02 critical Varcie 2.552 dia Mi-M2 = (Tu-k t ta (S? ni “หว. = (1757-64.3) +2.552 14.5+ + S.12 9 Iloce £ 5.551 limita lower Upper limit 114-5.5515.849 11.4+5.55 / 16.951 (ssue 5.849) < MM₂ < (16.951 [5.85 16.95 (2 decmais)