maths
posted by Washington .
A coin is biased so that a head is twicw as likely to occur as a tail. Suppose the coin is tossed three times.
What is the probality of getting at exactly two tails

p tails = 1/3
1/3 * 1/3 * 1/3 = 1/27 
what is the disadvanatage of using variance as a measure of dispersion