# A coin is tossed 4 times, what is the probability of NOT getting 2 heads?

Feb 21, 2016

Use the complement method ...

#### Explanation:

P(not getting 2 heads) = 1 - P(getting two heads)

Assuming a FAIR coin and using the BINOMIAL distribution ...

P(getting two heads) =(4!)/(2!xx2!)(1/2)^4=3/8

Finally, ...

P(not getting 2 heads) $= 1 - \frac{3}{8} = \frac{5}{8}$

hope that helped