View Full Version : Standard deviation need help to get started

04-28-2008, 09:04 PM
I need help getting started. I figured out the mean and the SD. I am just not sure how to start the formula for figuring out part a, b and c.

The fracture strength of a certain type of manufactured glass is normally distributed with a mean of 579 MPa with a standard deviation of 14 MPa.
Find the z-score for each question as z=(x-mean)/sd

(a) What is the probability that a randomly chosen sample of glass will break at less than 579 MPa?

(b) More than 590 MPa?

(c) Less than 600 MPa?

04-28-2008, 10:42 PM
These are the simplest possible statistics questions. You must not be struggling with these. They are lookup questions.

Use your formula and find the standard z-score in each case. There is nothing else to these. You should have a table of values or a calculator.

Really, if you remain confused by these for more than 2 days, you need to go have a chat with your academic advisor. This just won't do. Have you been attending class and reading your materials?