Question

B:)) "Determine the mean and standard deviation of the random variable X. Round your results to the nearest penny."

Answer 1

do you know the formula?

Answer 2

Yes it's like... Standard Deviation over the sample...

Answer 3

Unless I'm wrong...

Answer 4

its same

what do you get for mean?

Answer 5

\(\mu = mean = \sum p_ix_i \\ \sigma = \sqrt{\dfrac{1}{N}\sum (x_i-\mu )^2}\)

Answer 6

N would be what tho?...

Answer 7

number of samples, here it would be = 2

Answer 8

Ahh ok cuz we had 2 samples or whatever right?

Answer 9

for reference of others:
http://assets.openstudy.com/updates/attachments/56fe8aabe4b0261a951e1fdf-yanasidlinskiy-1459522239651-1.png

Answer 10

yes.

mean = 35*P(35) + (-1)P(-1) = ... ?

Answer 11

use the values we got from part (a)

Answer 12

Yea, that's what I'm doing rn

Answer 13

Okay, I'm not sure if I'm doing this right but I'm just gonna plug in the numbers, cuz I'm not confident about it.....
35*.0263(35)+(-1).9737(-1)

Answer 14

why 35 and -1 are multiplied twice?

Answer 15

Oh my bad lol

Answer 16

ohh.. P(35) is probability of 35, not probability*35

Answer 17

so,

mean is
35*(0.0263) + (-1)(0.9737) = ...

Answer 18

So, 1.9?

Answer 19

i get -0.0526...

Answer 20

What?

Answer 21

http://www.wolframalpha.com/input/?i=35*(0.0263)++%2B+(-1)(0.9737)+%3D+...

Answer 22

Desktop calculator... My laptop lol

Answer 23

now start calculating std deviation

Answer 24

Okay, my sample would be the same, right?

Answer 25

yes
same

Answer 26

Same formula as well, right?

Answer 27

Like.... Wait. Actually how would I calculate it.

Answer 28

This: \( \\ \sigma = \sqrt{\dfrac{1}{N}\sum (x_i-\mu )^2}\)

Answer 29

N = 2,

x1 = 35
x2 = -1
mu = -0.0526

Answer 30

\(\sqrt {\dfrac{1}{2} [(35-(-0.0526))^2+(-1-(0.0526))^2]}\)

just substituted the values

Answer 31

24.8?

Answer 32

you should get 24.797

try it
http://www.wolframalpha.com/input/?i=%5Csqrt+%7B%5Cdfrac%7B1%7D%7B2%7D+%5B(35-(-0.0526))%5E2%2B(-1-(0.0526))%5E2%5D%7D

oh yes, correct!

Answer 33

Gee, Okay, I may need to remember this ahha

Answer 34

the formulas, yes.

Answer 35

No, I know the formulas just messing with the numbers is really insane.

Answer 36

good luck!

Answer 37

Ughgh, yes thank you