# Analyse distribution of IQ scores in Americans

From a population of 25,000 Americans in 1969; it was discovered that their collective IQ Score mean was 105 with a standard deviation of 12.

a. how many IQ scores exceeded 115?

b. what is the probability of IQ scores that fell between 68 and 75?

c. how many IQ scores fell above 3 standard deviations?

d. what is the percentage of IQ scores less than 125?

e. find where the worst 70% of IQ scores fall?

f. to be considered a "genius"; an IQ score must exceed 145; how many made it?

g. find a 90% confidence interval?

h. how many IQ scores fall below 1 standard deviation?

i. find where the worst 10% of IQ socres will fall?

j. find the best IQ score?

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#### Solution Preview

There are many ways in which you can calculate using the computer. If you want to use excel, there is a very good tutorial on http://www.dacc.edu/~dyork/normal_distribution.htm. It tells you how to input the parameters.

If you are not asked to use excel explicitly, I suggest that you use this online calculator, much easier than excel. ...

#### Solution Summary

The expert analyzes the distribution of IQ scores in Americans. The percentages of IQ scores less than 125 are determined.