Conditional Probability!

Probability as you is the odds of something happening wheather it favors the event or not. A favorable even is when the number of wanted outcome is greater than 50. Probability is commonly written as a fraction or sometimes even a percentage. In the case of doing mulitile probabilities it is easier just to write things as a decimal, so that is the way its done. To do mulitiple probabilities you must draw a tree.

*Probability tree- A tree drawn to show and or help find probabilities. Can be drawn with decimals, percentages or fractions. It has as many branches for as many kinds of probability you need to find. It has as many sets of branches for as many times that you need to find this probability.

*To make a tree for multiple probabilites you must make sure that the branches in each set add up to 10. And each number of sets under that doubles in count of sets. Still each set must equal 10.

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Example 1:


a) P(X') = .6
b) P(Y'/X)= .4 x .7 = .28/.4 = .7
c) P(Y'/X')= .5 x .6 = .3/.6 = .5
d) P(X and Y)= .4 x .3 = .12
e) P(X' and Y)= .6 x .5 = .3
f) P(Y)= .12 + .3 = .42
g) P(X/Y)= .12/.42 = .286
h) P(X'/Y)= .3/.42 = .714