Question

check part C
I got 0.8 the first time and the second time i got 1.3

Answer 1

Ps.- sorry i cut off part C a little bit, but it says 1.3

Answer 2

is your mean correct?

Answer 3

yes it should be

Answer 4

mean = (sum)/total numbers

= (0+1+2+3+4)/5
isn't it ?

Answer 5

yes

Answer 6

mean = Just add up all the numbers, then divide by how many numbers there are

Answer 7

so isn't mean = 2 ?

Answer 8

i got this- 4*0.2 + 3*0.25 + 2*0.3 + 1*0.1 + 0*0.15

Answer 9

= 2.25

Answer 10

also thats not the way you calculate std deviation or mean

thats just \(\sum x_i\times i\)

Answer 11

ok then im worng and your right

Answer 12

you have the formula of std deviation with u ?

Answer 13

Howard did it correctly when finding the mean
when the values have different probabilities , you do what he did. and get 2.25

(the "simple formula" assumes equal probabilities = 1/n )

Answer 14

so B is 2.25 ?

Answer 15

mean "grade" was asked...thats why I thought

Answer 16

anyways,
then yes, 2.25 is correct...sorry

Answer 17

i think it means grade level i hope but 0 isnt a grade lvl

Answer 18

ok, now std deviation

N=5,
(x_i)s are your P(X) values
\(\mu \) is the mean = 2.25

Answer 19

Var[X] = sum((X - E[X])^2*P[X]) = sum(X^2*P[X]) - E[X]^2 =
= 16*0.2 + 9*0.25 + 4*0 .3 + 1*0.1 + 0*0.15 - 2.25^2 =
= 6.75 - 5.0625 = 1.6875
StDev[X] = sqrt(Var[X]) = 1.3.

i could of messed up i did this a few times on paper and on mathway

Answer 20

you forgot to divide by N ?

Answer 21

Also, you didn't distribute the sum..
\(\sum \mu^2 = n\mu^2 \)

Answer 22

i'd say, use the formula you attached....and not what u have done

Answer 23

yes, I get 1.299 for sigma

Answer 24

http://www.wolframalpha.com/input/?i=%28.2*4^2%2B.25*3^2%2B.3*2^2%2B.1*1^2%2B.15*0^2%29-2.25^2

Answer 25

sqrt( sum ( (x - mu)^2 * P(x) ))

Answer 26

i need to refresh on this topic :P

Answer 27

that simplifies for equal probability to
sqrt( sum ( (x-mu)^2 * 1/n) )
or
\[ \sqrt{ \frac{1}{n} \sum (x_i-\mu)^2 }\]

Answer 28

ok so i am also right on C? thakn you guys for helping me