Suppose that an anxiety measure has a mean of 119 and variance of 324.00.

Question

The researcher only wants to work with 79% of the upper participants. What is the smallest average score the researcher should consider with a sample size of 32?

Answer 1

The Mean of 119 and Variance of 324 relate to the population distribution. Since we're working with a sample, we need sample parameters. The Mean of the sample is still 119. The Standard Error (term for standard deviation of the sample) is calculated as follows. First find the standard deviation of the population which is the square root of 324, which equals 18. The Standard Error is 18 divided by the square root of 32, which equals 3.18.

Now we are looking for the point on the normal curve which has 79% of the distribution to the right. We can use InvNorm(0.79, 119, 3.18, RIGHT) = 116.4