Topic 13/14 Hypothesis Testing by Chi Square Test/Population Genetics

goodness of fit test

helps us judge if data that we observe fits expectations based on a current scientific theory

Chi-square test

evaluates how big the deviation of our observed data vs the expected data is

test statistic

measure of the degree of deviation between observed and expected

observed (data)

actual data collected when doing the experiment

expected (data)

what you would see if the results of the experiment were exactly as predicted by theory

null hypothesis

the data are consistent with the specified distribution

alternative hypothesis

the data are not consistent with the specified distribution

p-value

probability that the null hypothesis is true

degrees of freedom

represent the number of independent values that can vary in the calculation of the chi-square

=(number of categories) – 1

reject the null hypothesis

difference between observed and expected is just too great to be just due to sampling variation

p-value is very low

fail to reject the null hypothesis

we don’t have a good basis for throwing out the current theory

p-value is not very low

population

group of individuals of the same species who interbreed or can potentially interbreed

phenotype frequency

portion of the individuals in a population that have a given phenotype

genotype frequency

portion of the individuals in a population that have a given genotype

allele frequency

fraction, out of all of the copies of a given gene, that are of a given allele

allele counting method

1. Count the number of copies of a given allele in a population.

2. Divide this by the total number of copies.

Hardy-Weinberg equilibrium

allele and genotype frequencies in a population will remain constant from generation to generation in the absence of other evolutionary influences

Hardy-Weinberg equation

relates allele frequencies to genotype frequencies in a population

random mating

gene being considered does not influence mating

selection

genotype gives a greater chance of successfully producing surviving offspring

migration

introduction of individuals from a different population