Two coin are tossed 4 times ,find?

[mattamimi]

1)the probability of 2 heads in 4 times ?
2)the probability of less than one head once?
3)the probability of more than 2 tails in 3 times ?
4)the expected number of two tails ?
5)the variance of the number of 2 heads

 

[Mark44]

1)the probability of 2 heads in 4 times ?
2)the probability of less than one head once?
3)the probability of more than 2 tails in 3 times ?
4)the expected number of two tails ?
5)the variance of the number of 2 heads

What have you tried?

 

[Redbelly98]

Note, here is the active thread for this problem:
https://www.physicsforums.com/showthread.php?t=401476