A sample of 16 students is taken. The average age in the sample was 22 years with a standard deviation of 6 years. Construct a 95 % confidence interval for the average age of the population.

Solution: Similar to the previous problem, a 95% confidence interval for the mean of the population is given by

where corresponds to the sample mean, corresponds to the standard deviation, corresponds to the sample size and corresponds to the cutoff point to the standard normal distribution. Since we want 95% confidence interval, we take, and then we look up the normal distribution table to get that. Replacing all this information in the equation we obtain: