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@jim_thompson5910 can you help me please?

X = number of correct questions
|dw:1433396801483:dw|

multiply X and P(X) to form the X*P(X) column of values

good

now add up the values in the X*P(X) column and you will get the expected value

ohhh ok thanks!

now onto the second part "What are the variance and standard deviation? "

you're going to have 2 additional columns. I'm going to erase the X*P(X) column to make room

instead I'm going to have X - mu and (X - mu)^2
|dw:1433397803766:dw|

mu = expected value = 0.5

oh wait, there's one more column needed
the P(X)*(X-mu)^2 column
|dw:1433397806736:dw|

oh ok, so do i find the mean of p(x)?

you're asking about the value of mu?
mu = 0.5 and it was found when you computed the expected value

oh ok sorry it took me a while to calculate the numbers

this is what I'm getting

I see the typo you made. Look at the bottom row, last column

you should have (2-0.5) and not (1-0.5)

sorry i pasted the wrong table this is what i got

btw if you have excel or open office (it should work in there too), you can type in formulas like you see attached

that way you can automate things a bit

Ok thanks

now add up everything in the P(X)*(X-mu)^2 column, you should get 0.375

0.375 is the variance
take the square root of the variance to get the standard deviation

standard deviation= .61237243569
variance= 0.375

looks good

were you able to get started on this one? or no?

sort of but I'm not sure if i did it right, i did

I made question 1 have P(correct) = 0.33
and question 2 has P(correct) = 0.25
|dw:1433401116557:dw|

are you seeing how I'm getting these values?

ohhh yes thanks!

so here is getting 0 questions correct
|dw:1433401932751:dw|
ie getting both wrong

0.0825 is cut off, but that's getting both correct
|dw:1433401967587:dw|

Ok so 0.5025 is the probability of getting 0 correct and 0.0825 is getting both correct.

yes

Ok so would i need to find the expected value again?

this is what I get

You have 0.825 instead of 0.0825

that's fine, it doesn't matter about the medal thing lol

I'm glad it's making sense now