Thread: Confidence intervals

Q. It is known that the mean length of a nail being produced is 5.69 mm. If a sample of 19 nails are measured, and is found to be normally distributed with a mean value of 5.76 mm with a standard deviation of 0.15 mm.
Test to a statistical significance of 95% that these 19 specimens come

from the parent population.

What equation do i use for this?

s=0.15,n=19,x=5.76,95%=1.96

5.76 -1.96(0.15)/SQRT(19)

5.76 +1.96(0.15)/SQRT(19) ?