Question

can someone Check my answer to this question please
Grades can be converted into numbers (as in calculating a GPA A=4 B=3 C=3 D=1 F=0
X(grade) 4 3 2 1 0
P(X) .20 .25 .30 .10 .15
A) Verify that this is a legitimate probability distribution.
B) Find the mean grade for this class
C) Find the Standard deviation

A) check it equals 1
B) do i add 4+3+2+1?
C) i should find the standard deviation for what?

Answer 1

@ganeshie8 can you help me please

Answer 2

A) Verify that this is a legitimate probability distribution.
that means the sum of the P(x) is 1, and it does.

B) Find the mean grade for this class

assuming the class received the grades with the probability given by P(x)
example: 20% of the class received an A
you multiply each grade number by its probability and sum to get the mean value

Answer 3

C) Find the Standard deviation

they mean the std of the grades
the formula for the std is
\[\sigma=\sqrt{\frac{ 1 }{ N } \sum_{i=1}^{N}(x_i- \mu)^2}\]

where N is the number of grades , mu is the mean (from step B,