Question

determine both the lower and upper limits of a 90% z-confidence interval for µ , the mean score for all students in the school district who are enrolled in gifted and talented programs.

Answer 1

CI = ( μ - 1,64 * σ /√n ; μ + 1,64 * σ /√n )

Explanation:

We assume Normal Distribution

For Confidence Interval, CI = 90 % and α = 10 %

α = 0,1 and α/2 = 0,05

So we will look for z score reciprocate to these values, at the two tails of the bell

z(α/2) = 1,64 at th right tail and -1,64 at the left

CI = ( μ ± 1,64 * σ /√n )

CI = ( μ - 1,64 * σ /√n ; μ + 1,64 * σ /√n )