Aconfidence interval estimate is desired for the gain in a circuit on a semiconductor device. assume that gain is normally distributed with standard deviation σ = 15. (a) how large must n be if the length of the 95% ci is to be not greater than 30? (b) how large must n be if the length of the 99% ci is to be not greater than 30?

(a) n≥4 (b) n≥7

Step-by-step explanation:

The confidence interval is defined as

So the difference between upper limit (UL) and lower limit (LL) must be

We can clear the number of observations rearranging the last equation

(a) UL-LL must be less than 30. For a 95% CI, z=1.96.

The sample needs to be at least 4 observations.

(b) UL-LL must be less than 30. For a 99% CI, z=2.576.

The sample needs to be at least 7 observations.

the answer is (-4,-4)

hope this ! : d