Question

Determine the confidence level for each of the following large-sample one-sided confidence bounds. (Round your answers to the nearest whole number.) (a) Upper bound: x + 1.28s/Vn (b) Lower bound: x - 1.88s/Vn (c) Upper bound: x + 1.04s/Vn

Answer 1

These are single tailed values of alpha. I have used the z tables. We can also use excel function NORMSDIST and get the left tailed values, and multiply by 100 to get the answers.

(a) Zcritical = 1.28, From the z tables, the p value = 0.8997. Therefore confidence level = 89.97% $\approx$     90%

(b) Zcritical = 1.88, From the z tables, the p value = 0.9699. Therefore confidence level = 96.99% $\approx$ 97%

(c) Zcritical = 1.04, From the z tables, the p value = 0.8508. Therefore confidence level = 85.08% $\approx$    85%