October 10, 2015

Homework Help: Probability

Posted by Sue on Tuesday, December 5, 2006 at 1:25am.

Using standard deviation. Normally distributed mean of 0 degrees standard deviation of 1.00 degrees celcius.

1. between 0 and 1.28

2. greater than 0.37

3. less than -0.92

4. between 1.50 and 2.50

5. between -0.90 and 1.95

6. less than 0

I don't know how to solve these problems.

They are asking for the fraction of the distribution that lies within each of the stated intervals. You can solve these with a table lookup of the normal distribution function, which should be explaied in your text, or by using the handy Java computional tool at

For the first problem, enter 1.00 for the standard deviation, 0 for the mean, and integration limits "start" and "end" of 0 and 1.28, and then hit the "enter " key. I get 39.97% for that one. The last one (6) is 50%, since the distribution curve is symmetic and you are taking the integral under the curve beyond the mean value. For (4), I get 6.06%. When you are only given one limit, such as in problem (3), take a large number like -10 (ten standard deviations) as the lower limit, since you cannot enter minus infinity as a limit.

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