Four coins

• December 16th 2009, 11:28 AM
nafiro
Four coins
If you were to toss four coins, what are the odds in favor of at least two landing heads up?
• December 16th 2009, 12:09 PM
ANDS!
What is the sample space of four coins being tossed:

HHHH, HHHT, HHTH, HTHH, THHH. . .etc. Now of those how many have at least two H's in them?

Or, if you have studied the binomial formula, you recognize this as a binomial distribution with four independent trials (the individual coins being tossed).
• December 16th 2009, 12:11 PM
pickslides
Let X be the probability of tossing heads

Then $P(X\geq 2) = P(X= 2)+P(X= 3)+P(X= 4)$