Question

Bruce Tay, intern at Mark-Analytics, is conducting a study in which a population mean will be estimated using a 92% confidence interval. The estimate needs to be within 15 of the actual population mean. The population standard deviation is estimated to be around 60. The necessary sample size should be at least (round up!): answer .. The weights of aluminum castings produced by a process are normally distributed. A random sample of 6 castings is selected; the sample mean weight is 1.8 pounds; and the sample standard deviation is 0.12 pound. The 90% confidence interval for the population mean casting weight is: lower upper answer ľ You are evaluating the service level provided to walk-in customers. Accordingly, you recorded the waiting times for 64 randomly selected walk-in customers and determined that their mean waiting time was 16 minutes. Assume that the population standard deviation is 4 minutes. The 90% confidence interval for the population mean of waiting times is: lower upper answer

Answer 1

1) The required sample is. Margin error(E)=15 Standard deviation=60 = (1-75560) [From z-able =an=1.75] = 49

2) Given, n-6 T-1.8 5 -0.12 The 90% confidence interval for the mean is, 1.8-2.0150723) <u<1.8+2.015072 [Using t-table, th=2015] 1.8 -0.0987 <u<1.8+0.0987 1.7<u<1.9 Answer: Lower = 1.7 and Upper = 1.9

Given, n = 64 1-16 The 90% confidence interval is, 16–164 La } <»<16+1.64() (Using 2 table zog =1.64] 16-0.82 < u <16 +0.82 15.18 < u <16.82 Answer: Lower = 15.18 and Upper = 16.82