confidence interval

An athlete wishes to estimate the mean number of miles run by him per day during practice session. The number of miles run by him on 7 days selected randomly is 7.2, 7, 7.5, 7.8, 7.6, 8 and 7.5. Based on the sample mean, what is the point estimate of the mean? Find the 95% confidence ..

An obesity clinic states that the average weight loss after a 15-week program of regular aerobic exercise is 8 pounds with a standard deviation of 2.8 pounds. To test this report, a statistician selected 55 people doing regular aerobic exercise and found the average weight loss as 7.4 pounds. Is th..

A cement manufacturer claims that the maximum final setting time of cement is 10 hours. A sample of 13 bags were tested and found that the mean of the maximum final setting time was 11.2 hours with a standard deviation of 1.8 hours. At α = 0.01, can the claim be rejected? Also find the 99% ..

A survey report states that the average coffee consumption of the American adult is 400 cups per annum. The annual coffee consumption of 25 American adults was subjected to a study and it was found that the sample has a mean of 418 cups with a standard deviation of 12 cups. At α = 0.10, can t..

Based on a sample of 150 students at a university, it was found that 112 of those students walk or use bike to travel to university. Construct a 95% confidence interval for p , the proportion of all students who use bike or walk to school. => 71.5% < p < 78.5% or 70% < ..

A sample of 10 mathematics books of grade 7 had the following number of pages. Find the 98% confident interval for the variance of the pages. Assume that the variable is normally distributed. 1000 1320 590 820 1150 1570 1090 1585 995 1285 => between 38110 and 345769 or between 4..

A manufacturer claims that the rods manufactured in their factory have a diameter of 8.5 cm. A random sample of 80 similar iron bars were tested and found that the mean diameter is 8.43 cm and the variance is 0.032 cm 2 . Is there enough evidence to conclude that the diameter of the iron bars is no..

A teacher wishes to estimate the average weight of 10 students of grade 6 taken randomly. The weight(in pounds) of the students are shown. Find the 99% confidence interval for the variance for the weights of students. Assume that the variable is normally distributed. 90 88 96 85..

A researcher wishes to estimate the average daily wage (industrial composite) of industrial workers. A previous study showed that the standard deviation is $23. How large a sample must be selected if he wants to be 99% confident of getting an interval that contains the true mean..

The total expenses (in billion dollars) for recreation spent for a period of 10 consecutive years by a country are shown here. Find the 98% confidence interval for the standard deviation. Assume that the variable is nomally distributed. 13 14.1 15.2 16.2 16.9 17.3 18.3 19.9 20.7..