# Genetics Probability review.txt

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1. probability
• P(E) = m/n
• m= #desired outcomes
• n= total # of outcomes
2. Independence
• if the occurrence of one event does not effect the probability of the other
• ie: probability of first having a boy, then having a second child a boy (1/2)
• the "or" rule
• P(A or B) = P(A) + P(B)
• ie: probability of rolling a 5 or 6 on die (1/6 + 1/6) = 2/6 = 1/3
4. Multiplication rule
• the "and" rule
• for independent events..the probability of BOTH events occurring
• ie: probability of A_bb from a AaBb x AaBb dihybrid cross
• P(A_) * P(bb) = 3/4 * 1/4 = 3/16
5. Binomial expansion
• Used for calculating the probability of MULTIPLE outcomes occurring
• 1. Calculate the # of outcomes that satisfy the question
• 2. Probability of each permutation
• P(outcome) = (n!/a!*b!)p^a * q^b
• n = # of trials
• a = # of p results
• b = # of q results
• p = probability of a
• q = probability of b
• ie: if Aa x Aa have 4 kids, what is the prob of getting 3 A_ and 1 aa?
• P = (4!/3! * 1!) (3/4)^3 * (1/4)^1
• P = 27/64
6. Binomial Expansion w/MULTIPLE terms
• P = (n!/a!b!c!d!)p^a * q^b * r^c * s^d
• a+b+c+d = n
• q+r+s+t = 1
7. Outcomes
• formula for how many outcomes are possible (ie: how many combinations of 2 hats you can pick out of a set of 5)
• nCr = n!/(n-r)! * r!
• n = total number
• r = # of selections
• outcomes = 5! / (5-2) * 2! = 10
• ALTERNATE is Pascal's triangle:
• go to the 5th row, and count from left to right starting from 0, 1, 2 (end at 2 since you are picking 2 hats)
8. At Least One
• probability of At least one occurrence
• ie: probability of eldest girl of 3 children having AT LEAST ONE brother
• P = P(1st brother) + P(2nd brother) - P(both being brothers)
• P = 1/2 + 1/2 - (1/2*1/2)
• P = 1 - 1/4 = 3/4= 75%
9. Chi Squared test
• 1. add all X^2 values (each value is a n)
• X^2 = (O-E)^2/E
• 2. calculate degrees of freedom
• df = (n-1)
• 3. look at chart and see if is Greater than 0.05
• 4. If is greater than 0.05, then FAIL TO REJECT hypothesis (Ho)
• 5. If is .05 or less, then REJECT Ho and ACCEPT Ha (alternate hypothesis)
 Author: Anonymous ID: 105360 Card Set: Genetics Probability review.txt Updated: 2011-09-30 04:39:28 Tags: genetics Folders: Description: probability Show Answers: