Asample of 20 cigarettes is tested to determine nicotine content and the average value observed was 1.2 mg. compute a 99 percent two-sided confidence interval for the mean nicotine content of a cigarette if it is known that the standard deviation of a cigarette’s nicotine content is σ = .2 mg.

Step-by-step explanation:

Confidence interval for population mean is given by :-

, where = two -tailed z-value for (significance level)

n= sample size .

= Population standard deviation.

= Sample mean

By considering the given information , we have

n= 20

Using z-value table ,

Two-tailed Critical z-value :

The 99 percent two-sided confidence interval for the mean nicotine content of a cigarette will be :-

Hence, the 99 percent two-sided confidence interval for the mean nicotine content of a cigarette: