X = number of gallons needed to fill up, and its standard deviation is 0.02 Test statistic is the X-Bar, ie., the average number of gallons needed to fill up Sample size n is chosen to be 30, so X-Bar follows normal distribution, thanks to central limit theorem Standard Error = Standard Deviation of X-Bar = Standard Deviation of X / SQRT(n) 0.02/SQRT(30) = 0.003651484