Posted by **Jenn** on Monday, September 20, 2010 at 8:38pm.

Using the 68-95-99.7 rule:

Assume that a set of test scores is normally distributed with a mean of 100 and a standard deviation of 20. Use the 68-95-99.7 rule to find the following quantities:

Suggest you make a drawing and label first…

a. Percentage of scores less than 100

b. Relative frequency of scores less than 120

c. Percentage of scores less than 140

d. Percentage of scores less than 80

e. Relative frequency of scores less than 60

f. Percentage of scores greater than 120

- stats -
**PsyDAG**, Tuesday, September 21, 2010 at 11:27am
Do you know the rule? For example, 68% are with in one standard deviation of the mean in both directions, 95% are within 2 SD and 99.7% are within 3 SD.

a. in a normal distribution, mean = median. What does that tell you?

b. Mean + 1 SD = ?

I have started you out, but we do not do your work for you. Once you have answered your questions, we will be happy to give you feedback on your work. Although it might require more time and effort, you will learn more if you do your own work. Isn't that why you go to school?

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