Question

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 1

I thought it was C but i was wrong

Answer 2

I don't know how you are supposed to calculate things like mean and standard deviation, but I do this with my TI-84.
I put the results in list1 (L1) and then STAT-CALC-1var stats gives:

mean = 94.18 = m
stdev = 2.97 = s

The interval [m-s, m+s] = [91.2, 97.2]. Not enough.
The interval [m-2*s, m+2*s] = [88.2, 100.1]. Not enough. (see score: 88).
So it is 3 standard deviations! ANswer C is right.

If you round off: m = 94, s = 6, so 88 is counted in with [m-2s, m+2s].
In that case, answer A is "right".
Rounding off makes no sense imho.

Answer 3

ok thanks for your help

Answer 4

yw!

Answer 5

:)