1. Inferential Statistics

2. 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

3. 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.

4. 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.

5. 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.

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

7. 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