Scores on a standardized exam are known to follow a normal distribution with a standard deviation σ= 19. A researcher randomly selects 135 students and computes their average score. He reports that...

Scores on a standardized exam are known to follow a normal distribution with a standard deviation σ= 19. A researcher randomly selects 135 students and computes their average score. He reports that the mean score is 76.8, with a margin of error of 2.413.

How confident are you that the mean score for all students taking the exam is in the interval (74.387, 79.213)?

Confidence =               %