Thread: mean and standard deviation

If heads is a success when we flip a coin, getting a six is a success when we roll a die, and getting an ace is a success when we draw a card from an ordinary deck of 52 playing cards, find the mean and standard deviation of the total number of successes when we:
1. flip a balanced coin, roll a balanced die, and then draw a card from a well-shuffled deck;
2. flip a balanced coin three times; roll a balanced die twice, and then draw a card from a well-shuffled deck.

Originally Posted by TheHolly

If heads is a success when we flip a coin, getting a six is a success when we roll a die, and getting an ace is a success when we draw a card from an ordinary deck of 52 playing cards, find the mean and standard deviation of the total number of successes when we:
1. flip a balanced coin, roll a balanced die, and then draw a card from a well-shuffled deck;
2. flip a balanced coin three times; roll a balanced die twice, and then draw a card from a well-shuffled deck.

Each of these is the sum of three random variable for which you should be able to find the means and variances.

The mean of the sum of three RV is the sum of the means.

The variance of the sum of three RV is the sum of the variances.

and of course the standard deviation is the square root of the variance.

RonL

Ok, so for the very first part, the mean of flipping a balanced coin is 1/2?????? (E(X) where f(x) is 1/2 because that is the probability of getting heads and x is 1?) Sorry, but can you show me how to compute the mean and variance for just one of the parts? I am really not sure how to interpret this. I know it shouldn't be very hard.