sample mean

Radio tubes manufactured by a company are expected to have a mean lifetime of 400 hours, with a standard deviation of 30 hours. Random samples of 10 tubes were tested. It was found that 3 tubes had a lifetime of 398 hours, 5 of them had a lifetime of 410 hours and 2 had a lifeti..

A survey of software engineers having more than ten years experience finds the average salary to be $120,000. If the standard deviation for the sample of 40 software engineers was $12,000, construct a 99% confidence interval of the mean(μ) for all engineers. => 118,102.63 <..

Not all atoms of a given sample disintegrate together. Some atoms disintegrate right in the beginning for which the lifetime is zero. Therefore the lifetime of atoms, which disintegrate in between, ranges from zero to infinity...

The average intake of added sugars by a person is observed to be 68 gm/day for 10 days with a sample standard deviation of 2.86 grams. Find the 99% confidence interval of the true mean. => 65.1 < μ < 70.9 or 64 < μ < 01 or 67 < μ < 69 or 65 < μ &..

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? ..

A retail garment shop receives a shipment of trousers, with a standard length of 49.0 in. and a standard deviation of 1.0 in. A random sample of 32 trousers had a mean length of 48.8 in. State the null hypothesis(H o ) and alternative hypothesis(H a ). => H o : Mean le..

A four year public college or university charged a tuition fees of $10,903 in the year 2000, on an average. In 2001, a random sample of 10 four year public colleges or universities had a mean of $11,418 with a standard deviation of $650. At α = 0.01, find the test value an..

A manufacturer claims that the new nickel - metal hydride battery used in mobile phones has a talking time of 300 minutes before recharging. A researcher selected 45 samples with new battery and found that the mean talking time is 294.4 minutes with a standard deviation of 15.03..

In a study of reaction time to a medicine tested on a sample of 5 patients, an oncologist recorded the reaction times (in minutes) as 12, 20, 15, 28 and 30. Estimate the mean reaction time to the medicine with 95% confidence. => 11.2 < μ < 30.8 or 12 < μ < 30 o..

A nutritionist claims that the number of calories in one table spoon of the major brands of pancake syrup is 180. A sample of 18 major brands of syrup is selected and found that the mean number of calories in one tablespoon of syrup is 156 with a standard deviation of 54. At &al..