Question

Find the expected value of the number of questions you'd get right by guessing. What are the variance and standard deviation?

Answer 1

@jim_thompson5910 can you help me please?

Answer 2

X = number of correct questions

Answer 3

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

Answer 4

good

Answer 5

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

Answer 6

so the expected value is 0.5

which means, you expect (on average) to get 0.5 questions right if you randomly guessed

Answer 7

ohhh ok thanks!

Answer 8

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

Answer 9

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

Answer 10

instead I'm going to have X - mu and (X - mu)^2