An SRS of 450 high school seniors gained an average of ?¯=20 points in their second attempt at the SAT Mathematics exam. Assume that the change in score has a Normal distribution with standard deviation ?=49 . (a) Find a 95% confidence interval for the mean change in score ? in the population of all high school seniors. (Enter your answers rounded to two decimal places.) lower bound of confidence interval:     upper bound of confidence interval:     (b) What is the margin of error for 95% ? (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 95% confidence? (Enter your answer rounded to three decimal places.) margin of error:

Question

An SRS of 450 high school seniors gained an average of ?¯=20 points in their second attempt at the SAT Mathematics exam. Assume that the change in score has a Normal distribution with standard deviation ?=49 .

(a) Find a 95% confidence interval for the mean change in score ? in the population of all high school seniors. (Enter your answers rounded to two decimal places.)

lower bound of confidence interval:
 
 
upper bound of confidence interval:
 
 
(b) What is the margin of error for 95% ? (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 95% confidence? (Enter your answer rounded to three decimal places.)
margin of error:
 
 
 

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