Question

Statistics help?

Answer 1

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

Answer 2

wrong section

Answer 3

openstudy has a stats section?

Answer 4

could u do part a) ?

Answer 5

yeah

Answer 6

at the top it will say "Find More Subjects"

Answer 7

yeah, I know part a. It's legitimate because the total probability is equal to 1.

Answer 8

good, thats correct.
where r u stuck ?

Answer 9

Yeah its at the very bottom if you click on "Find More Subjects" at the top :))

Answer 10

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?

Answer 11

oh, whoops. i didn't see that before. i'll go there next time.

Answer 12

mean is 0.2 ?
which formula did u use ?

Answer 13

total is 1, divided by 5, .2? did i do that wrong?

Answer 14

yes...
Mean = \(\sum xP(x)\)
so, it will be
mean = 0.2*4 + 0.25*3 + ......

Answer 15

oooh. okay. one sec. let me calculate that. :P

Answer 16

2.25?

Answer 17

don't u have answers to verify ?

Answer 18

yeah, even i get 2.25

Answer 19

nope. answers are given upon completion. :P

Answer 20

but thanks, I think I got it now. Wrong formula. :P

Answer 21

and u know formula for sd ?

Answer 22

yeah, got that. i compared that with a friend, and she got the same answer. it was just the mean.

Answer 23

ok, good :)

Answer 24

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.