SOLUTION: You scored 88.7, 91.2, and 94.6 on your last three test scores. Find the standard deviation of your test scores. A. 0.95 B.1.22 C.2.42 D.4.35

Algebra ->  Probability-and-statistics -> SOLUTION: You scored 88.7, 91.2, and 94.6 on your last three test scores. Find the standard deviation of your test scores. A. 0.95 B.1.22 C.2.42 D.4.35       Log On


   

Question 89006: You scored 88.7, 91.2, and 94.6 on your last three test scores. Find the standard deviation of your test scores.
A. 0.95
B.1.22
C.2.42
D.4.35


Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
First lets find the mean:

To find the mean, add up all of the numbers and divide the sum by the number of numbers (which in this case is 3).
Mean=%2888.7%2B+91.2%2B+94.6+%29%2F3=274.5%2F3=91.5

So the mean is 91.5


Use this formula to find the standard deviation:

Standard Deviation: where is the mean, is the ith number, and is the number of numbers



So we can replace N with 3



Replace with 91.5



Expand the summation (replace each x%5Bi%5D with the respective number)




Subtract the terms in the parenthesis

sqrt%28%281%2F3%29%28%28-2.8%29%5E2%2B%28-0.3%29%5E2%2B%283.1%29%5E2%29%29

Square each term

sqrt%28%281%2F3%29%287.84%2B0.09%2B9.61%29%29

Add up all of the terms

sqrt%28%281%2F3%2917.54%29

Multiply

sqrt%285.84666666666667%29

Take the square root

2.41798814444295

So the standard deviation is 2.41798814444295

So if you round to the nearest hundredth, you get 2.42. So the answer is C)