Questions from Statistics Principles

Q: Find the 20th, 40th, 60th, and 80th percentiles of

Find the 20th, 40th, 60th, and 80th percentiles of the standard normal distribution.

Q: If Z is a standard normal random variable, what is the

If Z is a standard normal random variable, what is the probability that (a) Z exceeds .62? (b) Z lies in the interval ( -1 .40, 1 .40)? (c)|Z| exceeds 3.0? (d) |Z| is less than 2.0?

Q: A normal distribution with mean 11 5 and standard deviation 22 hundredths

A normal distribution with mean 11 5 and standard deviation 22 hundredths of an inch describes variation in female salmon growth in freshwater. (a) If a newly caught female salmon has growth 108, wha...

Q: Given the following probability distribution concerning the number of Web sites visited

Given the following probability distribution concerning the number of Web sites visited almost every day: (a) Construct the probability histogram. (b) Find E(X), (2, and (.

Q: The bell-shaped histogram for the heights of three-year

The bell-shaped histogram for the heights of three-year-old red pine seedlings on page 1 79 is consistent with the assumption of a normal distribution having mean = 280 and sd = 58 millimeters. Let X...

Q: If X has a normal distribution with µ = 90 and (

If X has a normal distribution with µ = 90 and ( = 4 find b such that (a) P(X < b) .6700 (b) P(X > b) .0110 (c) P(IX - 90 1 < b) = .966 (d) Check all of your answers using software.

Q: Suppose that a student's verbal score X from next year's Graduate Record

Suppose that a student's verbal score X from next year's Graduate Record Exam can be considered an observation from a normal population having mean 499 and standard deviation 120. Find (a) P ( X > 60...

Q: The lifting capacities of a class of industrial workers are normally distributed

The lifting capacities of a class of industrial workers are normally distributed with mean 65 pounds and standard deviation 8 pounds. What proportion of these workers can lift an 80-pound load?

Q: Th e bonding strength of a drop of plastic glue is normally

Th e bonding strength of a drop of plastic glue is normally distributed with mean 100 pounds and standard deviation 8 pounds. A broken plastic strip is repaired with a drop of this glue and then subje...

Q: The scores on an examination are normally distributed with mean µ =

The scores on an examination are normally distributed with mean µ = 70 and standard deviation ( = 8. Suppose that the instructor decides to assign letter grades according to the following...