An srs of 400 high school seniors gained an average of x = 20 points in their second attempt at the sat mathematics exam. assume that the change in score has a normal distribution with standard deviation σ-51.
(a) find a 99% confidence interval for the mean change in score t, in the population of all high school seniors. (enter your answers rounded to two decimal places.)
lower bound of
interval upper bound of confidence interval:
(b) what is the margin of error for 99%? (enter your answer rounded to two decimal places.)
margin of error:
(c) suppose we had an srs of just 100 high school seniors. what would be the margin of error for 99% confidence? (enter your answer rounded to three decimal places.)
margin of