Inferential Statistics

Inferential statistics Use the sample to make inferences about the population Use at least two variables at a time Can never be sure that results in sample are 100% representative of population Instead, statistics tell us the probability that results in sample are true in population

Significance Levels p<.10 This means that the probability that the finding was by chance is less than 1 in 10. This indicates that there was a 'trend' in the data. It is not considered a significant finding, but it is encouraging enough to continue with the line of investigation. p<.05 This means that the probability that the finding was by chance is less than 5 in 100. This indicates that there was a significant finding in the data. You should certainly continue with this line of investigation. p<.01 or less This means that the probability that the finding was by chance is less than 1 in 100. This means that there was a highly significant finding in the data. You should continue with this research with considerable confidence.

Inferential Statistical Tests: Which Test? Variable 1 Variable 2 Test to use Statistic Continuous Correlation* r Categorical 2 categories IV DV T-test t 3 or more categories One-way ANOVA F Chi-Square* 2 * For Correlation and Chi-Square analyses, variables are not distinguished as IVs or DVs.

Does GPA Correlate With Self-Esteem? High Low Does GPA tend to increase in people with high self-esteem? Correlation coefficient indicates the degree of association between the two variables.

Two Features of a Correlation Perfect Moderate Weak + - Direction Strength

Chi-Square Females Males Can drive 10 Can’t drive Females Males Expected Results for Random Relationship between Gender and Ability to Drive Females Males Can drive 10 Can’t drive What if this is what we really found: Females Males Can drive 16 4 Can’t drive