Chapter 2.4-2.5 Probability Rules

Vocabulary flashcards covering probability theory, chi-square analysis, and binomial probability as applied to Mendelian genetics.

Product Rule (Probability)

The probability that two independent events both occur is the product of their individual probabilities; used to calculate combined outcomes in genetic crosses.

Sum Rule (Probability)

The probability of mutually exclusive outcomes equals the sum of their individual probabilities; used to add alternative genetic pathways.

Conditional Probability

Probability of an event given that another event has already occurred; updates likelihoods based on known information (e.g., phenotype given genotype).

Prior Probability

Probability of an outcome before a cross is performed or before observing data.

Chi-Square Test

Statistical test that compares observed frequencies with expected frequencies to assess goodness-of-fit to a hypothesis.

Degrees of Freedom (df)

Number of independent values in a calculation; for chi-square, typically equals the number of outcome classes minus 1 (n-1)

P Value

Probability, under the null hypothesis, of obtaining results as extreme or more extreme than observed; commonly compared to 0.05 for significance.

Null Hypothesis (Chance Hypothesis)

Assumes observed deviations are due to random chance; rejected if P < 0.05 in a chi-square test.

Binomial Probability

Probability distribution using two coefficients a and b, whose sum = 1 and whose products predict the probability of an event

Binomial Expansion

Expansion of (p + q)^n into a sum of terms with binomial coefficients to compute probabilities for n trials.

Pascal's Triangle

Triangle of binomial coefficients that provides the coefficients in the binomial expansion.

Binomial Coefficient (n choose k)

Number of ways to choose k successes from n trials; calculated as n!/(k!(n−k)!).

Expected Frequency

The frequency predicted by a probability distribution for each outcome class.

Observed Frequency

The actual number of occurrences recorded in an experiment.

Outcome Class

A grouping of outcomes that share the same count of a trait (e.g., number of yellow seeds in a pod).