Find the sample mean

Question

The Wechsler IQ test is designed so that the mean is 100 and the standard deviation us 15 for the population of normal adults. Find the sample size necessary to estimate the mean IQ score of professional pilots. We want to be 90% confident that our sample mean is within 3 IQ points of the true mean. Assume that sigma equal 15 and determine the requriment sample size. Do the sample size appear to be reasonable?

Answer 1

Step 1:

The mean of Wechsler IQ test desingned for adults μ is 100.

The standard deviation of Wechsler IQ test desingned for adults σ is 15.

90 % confidence interval of sample mean is less than 3 IQ.

Here margin of error E is 3.

Z for 90 % confidence interval is 1.65.

Margin of error : ,

where Z is the Z-score for 90 % of confidence interval.

σ is the standard deviation

μ is the mean

n is sample size.

Step 2:

Find the sample size.

Sample size of the Wechsler IQ test desingned for adults is 68.

Solution:

Sample size of the Wechsler IQ test desingned for adults is 68.

Comments

How would you do it on a TI -84 Caculator.