Question 626447: Mrs. Jones Algebra 2 class scored very well on yesterday’s quiz. With one exception, everyone received an A. Within how many standard deviations from the mean do all the quiz grades fall?
91, 92, 94, 88, 96, 99, 91, 93, 94, 97, 95, 97
A. 2
B. 1
C. 3
D. 4
Answer by ewatrrr(24785)   (Show Source):
You can put this solution on YOUR website!
Hi,
Mrs. Jones Algebra 2 class scored very well on yesterday’s quiz: 91, 92, 94, 88, 96, 99, 91, 93, 94, 97, 95, 97
With one exception, everyone received an A. Within how many standard deviations from the mean do all the quiz grades fall?
Mean = 93.9 , SD = 3.12 (Using Excel Data Analysis Tool)
(99-93.9)/3.12 = 1.6
(88 - 93.9)/3.12 = -1.89
all the quiz grades fall within 2 SD from the mean.
Important to Understand z -values as they relate to the Standard Normal curve:
Below: z = 0, z = ± 1, z= ±2 , z= ±3 are plotted.
Note: z = 0 (x value the mean) 50% of the area under the curve is to the left and 50% to the right
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