18. Company XYZ know that replacement times for the portable MP3 players it produces are normally distributed with a mean of 3.2 years and a standard deviation of 0.4 years. Find the probability that a randomly selected portable MP3 player will have a replacement time less than 2 years? Report your answer accurate to 4 decimal places

Leave all probabilities as percentages, define x on all problems with data. Simple random samples of high interest (8.9%) and low interest (6.3%) mortgages were obtained. For the 40 high interest mortgages, the borrowers had a mean FICO credit score of 594.8 and a standard deviation of 12.2. For the 40 low interest mortgages, borrowers had a mean FICO credit score of 785.2 and a standard deviation of 16.3. Use an alpha level of 0.01, and a two tailed test of hypothesis to test the claim that the mean FICO score borrowers with a high interest mortgage is the same as the mean FICO score of borrowers with the low interest mortgage.

Suppose that the lifetimes of a certain kind of light bulb are normally distributed with a standard deviation of  120  hours. If exactly  98%  of the bulbs die before  900  hours, find the mean lifetime of the bulbs. Carry your intermediate computations to at least four decimal places. Round your answer to at least one decimal place.

Solve question 9, Part A, Part B and Part C only.

A manufacturer knows that their items have a normally distributed lifespan, with a mean of 13.6 years, and a standard deviation of 1 years.If 7 items are picked at random, 6% of the time their mean life will be less than how many years?Give your answer to one decimal place.

68. A manufacturer knows that their items have a normally distributed lifespan, with a mean of 12 years, and standard deviation of 1.4 years. The 4% of items with the shortest lifespan will last less than how many years? (show all work) |