Consider the following test scores obtained by a class.

Question

Test score 90 80 70 60 50
Frequency 1 4 11 6 2

Find the standard deviation (rounded to the nearest hundredth).
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I've posted this question earlier and I'm still getting the wrong answer.
I don't know from what point I messed up.....

this is what I did.
Mean:
90+320+770+360+100 / 24 = 68.33

Deviation
469.59+136.19+2.79+69.39+335.99 / 24= 42.25

then square root of 42.45 is 6.5

but my answer came wrong. please help!
I can't move on to my next homework question because I keep getting this wrong :(

Answer 1

looks like you weighted the values for the mean, but not for the deviation.