chapter 15: data exploration pt. 2 (inferential statistics)

hde 120

empirical data

facts derived from experience

population

all members of some group

sample

subset of a population

statistic

a quantity computed from a sample

parameter

in statistics, a quantity computed from a population

sampling distributions

the distribution of means of samples from a population

standard error of the mean

the standard deviation of a sampling distribution

alternative hypothesis

statistical term for the research hypothesis

null hypothesis

the hypothesis that is of no scientific interest; sometimes the hypothesis of no difference

directional hypothesis

an alternative hypothesis that predicts that the results of one condition will be greater (or less) than another, rather than a prediction that they will simply differ

one-tailed hypothesis test

statistical test of a directional hypothesis

two-tailed hypothesis test

statistical test of a nondirectional hypothesis

type I error

rejecting a null hypothesis when it is true

type II error

accepting a null hypothesis when it is false

alpha

probability of a type I error

statistical significance

the probability that an experimental result happened by chance

effect size

strength of the relationship between independent and dependent variables

power

the probability of rejecting the null hypothesis when it is, in fact, false

chi-square statistic

AKA chi-square goodness-of-fit test OR chi-square test for independence

evaluates frequency data to establish whether two (or more) categorical variables are related. Null hypothesis is that is variables are independent of each other

expected frequencies

anticipated values of the frequencies based on probability resulting from theory

observed frequencies

actual frequencies obtained from a sample

contingency table

table designed to examine whether the rows and columns are related to each other. If the numbers in the columns show no significant relationship to those in the rows (e.g., they are not contingent on the rows), then the rows and column frequencies are not demonstrably related

ANOVA

the analysis of variance statistic tests whether the means of more than two groups are equal

grand mean

mean of all the data

between-conditions variability

way of estimating the variability of the population based on the variability between the groups

within-conditions variability

way of estimating the variability in the population based on the variability within the groups

F ratio

statistic associated with ANOVA that is a ratio of between-conditions variability to within-conditions variability

sum of square

a measure of the variability of the data; the sum of the squared differences of observations from the mean

degrees of freedom

number of values in a statistic that are free to vary, such as the number of groups or subjects

mean square

sum of the squares divided by the number of degrees of freedom; an estimate of variance