8.25 The average life of a bread-making machine is 7years, with a standard deviation of 1 year. Assumingthat the lives of these machines follow approximatelya normal distribution, find(a) the probability that the mean life of a random sam-ple of 9 such machines falls between 6.4 and 7.2years;(b) the value of x to the right of which 15% of themeans computed from random samples of size 9would fall.

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Answered: 8.25 The average life of a bread-making…

A First Course in Probability (10th Edition)

10th Edition

ISBN:9780134753119

Author:Sheldon Ross

Publisher:Sheldon Ross

Chapter1: Combinatorial Analysis

Section: Chapter Questions

Problem 1.1P: a. How many different 7-place license plates are possible if the first 2 places are for letters and...

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A company claims that the mean monthly residential electricity consumption in a certain region is more than 880 kiloWatt-hours (kWh). You want to test this claim. You find that a random sample of63 residential customers has a mean monthly consumption of 910 kWh. Assume the population standard deviation is 120 kWh. At α=0.10,
A person's blood glucose level and diabetes are closely related. Let x be a random variable measured in milligrams of glucose per deciliter (1/10 of a liter) of blood. Suppose that after a 12-hour fast, the random variable x will have a distribution that is approximately normal with mean ? = 82 and standard deviation ? = 22. Note: After 50 years of age, both the mean and standard deviation tend to increase. For an adult (under 50) after a 12-hour fast, find the following probabilities. (Round your answers to four decimal places.) (a) x is more than 60(b) x is less than 110(c) x is between 60 and 110(d) x is greater than 125 (borderline diabetes starts at 125)
A person's blood glucose level and diabetes are closely related. Let x be a random variable measured in milligrams of glucose per deciliter (1/10 of a liter) of blood. Suppose that after a 12-hour fast, the random variable x will have a distribution that is approximately normal with mean ? = 81 and standard deviation ? = 26. Note: After 50 years of age, both the mean and standard deviation tend to increase. For an adult (under 50) after a 12-hour fast, find the following probabilities. (Round your answers to four decimal places.) (a) x is more than 60(b) x is less than 110(c) x is between 60 and 110(d) x is greater than 125 (borderline diabetes starts at 125)
A person's blood glucose level and diabetes are closely related. Let x be a random variable measured in milligrams of glucose per deciliter of blood. After a 12-hour fast, the random variable x will have a distribution that is approximately normal with μ = 85 and σ = 25. After 50 years of age, both the mean and standard deviation tend to increase. What is the probability that, for an adult under 50 years old, after a 12-hour fast, x is less than 130?
If the random variable of X is normally distributed with a mean of 50 and a standard deviation of 10, approximately what % of all possible observed values of X will lie between 30 and 70.
A population X is normally distributed with mean 71.5 and standard deviation 8.6. For each of the following values of x, find the corresponding z-number. Round off your answers to two decimal places. (a) x = 90(b) x = 80(c) x = 75(d) x = 70(e) x = 60(f) x = 50
3.2/2
If the z-value for a given x of a random variable Z is z =1.06, and the distribution of X is normal with a mean of 60 and a standard deviation of 6, to what x-value does this z-value correspond?
Women's heights are normally distributed with a mean given by u = 63.6 in. and a standard deviation given by o = 2.5 in. (a) If 1 woman is randomly selected, find the probability that her height is less than 62.6 in. Enter a number correct to 4 decimal places: (b) If 52 women are randomly selected, find the probability that they will have a mean height less than 62.6 in. Enter a number correct to 4 decimal places:
A person's blood glucose level and diabetes are closely related. Let x be a random variable measured in milligrams of glucose per deciliter of blood. After a 12-hour fast, the random variable x will have a distribution that is approximately normal with μ = 85 and σ = 25. After 50 years of age, both the mean and standard deviation tend to increase. What is the probability that, for an adult under 50 years old, after a 12-hour fast, x is more than 60?

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