1. ANOVA

2. Conceptual Basics
One variable (Interval / Ratio level DV) – one group (No IV) – surveyed once:
One variable (Interval / Ratio level DV) – two groups (One categorical level IV with two groups (also called factors)) – each group surveyed once:
One variable (Interval / Ratio level DV only) – one group (No IV) – surveyed twice:
One variable (Interval / Ratio level DV) – more than two groups (One categorical level IV with more than two groups (also called factors)) – surveyed once:

3. Conceptual Basics – One Way ANOVA
Each group (factor) in the sample may feel differently about the dependent variable being measured (recall stratified sampling???)
Within each group (factor), the members amongst themselves may also feel somewhat differently about the variable being measured
Objective of the ANOVA –

4. Conceptual Basics – One Way ANOVA
Differences between groups – sums of squares between factors
D.f. are number of factors – 1
Ratio gives you Mean sums of squares for numerator (MSS n)
Differences within groups – sums of squares within factors
D.f. are sample size – number of factors
Ratio gives you Mean sums of squares for the denominator (MSS d)
Ratio of MSS n and MSS d gives you the observed test statistic (the F ratio)

5. Conceptual Basics – One Way ANOVA
The Observed test statistic (F ratio)

6. Conceptual Basics – One Way ANOVA
The critical test statistic (critical F ratio)
Becomes smaller as sample size increases but larger as number of groups/factors increase
If observed F > critical F, reject the Ho
If observed F < critical F, accept the Ho