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.

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

Step-by-step 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 )