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Grades can be converted into numbers (as in calculating a GPA) where an A = 4, B = 3, C = 2, D = 1, and F = 0. For a fictional class, the grade distribution was: X(Grade) 4 3 2 1 0 P(X) 0.20 0.25 0.30 0.10 0.15 a) Verify that this is a legitimate probability distribution. b) Find the mean grade for this class. c) Find the standard deviation
openstudy has a stats section?
could u do part a) ?
at the top it will say "Find More Subjects"
yeah, I know part a. It's legitimate because the total probability is equal to 1.
good, thats correct. where r u stuck ?
Yeah its at the very bottom if you click on "Find More Subjects" at the top :))
finding the mean/sd. i found those out, but idk how to corrleate them with the grades. i know mean is .2, so would that mean the average grade is 4 because its' probability is .2?
oh, whoops. i didn't see that before. i'll go there next time.
mean is 0.2 ? which formula did u use ?
total is 1, divided by 5, .2? did i do that wrong?
yes... Mean = \(\sum xP(x)\) so, it will be mean = 0.2*4 + 0.25*3 + ......
oooh. okay. one sec. let me calculate that. :P
don't u have answers to verify ?
yeah, even i get 2.25
nope. answers are given upon completion. :P
but thanks, I think I got it now. Wrong formula. :P
and u know formula for sd ?
yeah, got that. i compared that with a friend, and she got the same answer. it was just the mean.
ok, good :)
hartnn, if you don't mind could you explain how to find the standar deviation, i'm a bit confused on how to go about it.