Standard Normal Random Variable
Date: 04/19/99 at 11:07:42 From: lorianne lowe Subject: College statistics 124 I need serious help. Q: Find each of the following for a standard normal random variable Z. (a) P( -0.65<Z<1.70 ) (b) P( Z > -1.03 ) I need to be shown how to do this in steps.
Date: 04/19/99 at 18:03:33 From: Doctor Pat Subject: Re: College statistics 124 Lorianne, I assume you have either a z-table or a calculator that will give you the probabilities for each z-score. A) Find the probability of Z in an interval P( -0.65<Z<1.70 ) Step one: find the area left of the lefthand interval limit (that is, look up the value under a z-score of -.65 in the table. It should be about .258. This means that about 25% of the values are to the left of this value (-.65) and about 75% are to the right.) Step two: find the area to the left of the righthand interval limit (1.70). This should be about .955 indicating that 95% of the z-values are smaller and about 5% are larger. Step three: since we want the probability between these, we subtract the area left of -.65 from the area left of 1.70 and get the area between them. In your problem, .955-.258 gives about .697 . B) To find the probability of Z > -1.03 find the probability that Z is less than that by looking up the value in the table; then subtract the answer from 1 since the total probability is one. Hope this helps. - Doctor Pat, The Math Forum http://mathforum.org/dr.math/
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