A consumer advocate analyses the nicotine content in some brand of cigarettes. A sample of 20 cigarettes of that Brand was analyzed which resulted in mean of 1.68mg. It is known that population...

A consumer advocate analyses the nicotine content in some brand of cigarettes. A sample of 20 cigarettes of that Brand was analyzed which resulted in mean of 1.68mg. It is known that population standard deviation is 18. Nicotine content is assumed to be normally distributed. Find the 90% confidence interval for the true average nicotine content in that brand of cigarettes. (clearly write down the formula first and then calculate)Also, Interpret the meaning of confidence interval.