3. The lifetimes (in months) of television picture tubes have an approximately normal distribution. A random sample of 15 television sets was selected and the lifetime of the picture tubes were measured. The mean of the sample was 96 months and the sample standard deviation was 2.93. point estimate of the population mean: = symbol number from problem point estimate of the population standard deviation: = symbol number from problem Find a 90% condence interval for the true mean of the lifetime of the picture tubes: 4. A television sports commentator wants to estimate the proportion of citizens who follow professional football. How many citizens must he sample to be within 2.5 percentage points of the true proportion with 94% condence? Write the formula and Show your work!! {:12