Scores on an achievement test had an average of 70 and a standard deviation of 10. Serena's score was 85. Assuming the scores have approximately a normal distribution, about what proportion of students scored lower than Serena?
A) 0.93
B) 0.07
C) 0.84
D) 0.68

Question

Quizplus · Accepted Answer

Serena's score is 1.5 standard deviations above the mean (85 - 70 = 15, 15/10 = 1.5). In a normal distribution, about 93% of the data falls below a score that is 1.5 standard deviations above the mean.

Scores on an Achievement Test Had an Average of 70