In: Statistics and Probability
the probability that the weather will be cold on sunday is .75 if the weather is cold there is a probability of 0.30 that barney wins if the weather is not cold there is a probablity of 0.90 that fred will win
what is the probability
barney wins the match
fred wins the match
P[ the weather will be cold on Sunday ] = 0.75
P[ the weather will not be cold on Sunday ] = 1 - P[ the weather will be cold on Sunday ] = 1 - 0.75 = 0.25
P[ Barney wins | the weather will be cold on Sunday ] = 0.3
P[ Fred wins | the weather will be cold on Sunday ] = 1 - P[ Barney wins | the weather will be cold on Sunday ] = 1 - 0.3 = 0.7
P[ Fred will win | the weather will not be cold on Sunday ] = 0.9
P[ Barney will win | the weather will not be cold on Sunday ] = 1 - P[ Fred will win | the weather will not be cold on Sunday ] = 1 - 0.9 = 0.1
P[ Barney wins and the weather will be cold on Sunday ] = P[ Barney wins | the weather will be cold on Sunday ]*P[ the weather will be cold on Sunday ]
P[ Barney wins and the weather will be cold on Sunday ] = 0.3*0.75
P[ Barney wins and the weather will be cold on Sunday ] = 0.225
P[ Barney will win and the weather will not be cold on Sunday ] = P[ Barney will win | the weather will not be cold on Sunday ]*P[ the weather will not be cold on Sunday ]
P[ Barney will win and the weather will not be cold on Sunday ] = 0.1*0.25
P[ Barney will win and the weather will not be cold on Sunday ] = 0.025
P[ Barney wins ] = P[ Barney wins and the weather will be cold on Sunday ] + P[ Barney will win and the weather will not be cold on Sunday ]
P[ Barney wins ] = 0.225 + 0.025
P[ Barney wins ] = 0.250
P[ Barney wins ] = 0.25
P[ Fred wins ] = 1 - P[ Barney wins ]
P[ Fred wins ] = 1 - 0.25
P[ Fred wins ] = 0.75