Question

Question 2 A tire manufacturer claims that their tires have an average life of more than 12000 km. A random sample of 20 tires has an average life of 12110 km with a standard deviation of 185 hours. Assume that the life of tires is normally distributed. What is/are the critical value(s)? Use 0.05 Answer: 1.7291 Question 3 We estimate population parameters by using a) only point estimates deviation d) point and interval estimates Answer: d b) only interval estimates c). the population standard Question 4 A confidence interval estimate is A. a point estimate estimate which of the following is correct? a) A and B b) B only cB and C d) B, C, and D Answer: c B. an interval estimate C. constructed around a point D. a single number Question 5 The critical value corresponding to a right tail area of 2.5% in a standard normal distribution will approximately be a) 1.96 Answer: a b) 2.58 c) 0.99 d) 1.64 Question 6 The left tail area corresponding to a critical value of -1.88 in a standard normal distribution will approximately be a) 0.9699 Answer: b b) 0.0301 c 1.9699 d) 1.0301 Question 7 The management of the company wishes to be 98% confident that one of their sample means is correct to within +S30 of the population mean. A previous study indicates that the standard deviation is approximately $293. How large a sample is necessary? Answer: 517

Answer 1

3) Lek X dendes the life Cen km) ots tyres no teak Ho: 시: 12000 again ak Hi! 시 > 12000 Here σ-21s unknsusn So, appr semata tost statistic is Ra sample mean s sample sd 七n-t under Ho ~