Chapter 15: One Way ANOVA Flashcards
Analysis of Variance (ANOVA) uses ___ as the statistic to evaluate the null hypothesis.
- variance
The ANOVA is a test used to analyze experiments that have more than ___ groups.
- 2
We use the ___ test to tell us whether there is a significant difference between any of the groups.
- F test
What does the alternative hypothesis state?( think means as a hint)
at least one of the conditions has a different effect than at least one of the other conditions. Thus, at least one of the group means is different from at least one of the other group means.
What does the null hypothesis state?
the different conditions are all equally effective, so, scores in each group are random samples from populations having the same mean value. aka there is no difference between any of the groups means
U1=U2=U3
Is there always variability within data?
yes
The ANOVA splits the total variance into two sources. What are they?
SStotal =?
- within- groups variance (SSw)
- between groups variance ( SSbtwn)
- SStotal = SSw + SSbtwn
What is MSw and MSbtwn?
- MSw is the estimate based on the within-groups variance and MSbtwn is the estimate based on between-groups variance.
What is the decision rule?
- If Fobt> Fcrit, reject Ho
- If Fobt< Fcrit, retain Ho
List the steps in order to calculating a 1 way ANOVA! (6)
1. Calculate the sum of squares L> SSw, SSbtwn and SStotal 2. Calculate the degrees of freedom (df) L> dfbetween = K-1 (k=number of groups) L> df within = N-K L> df total= N-1 **also df total= df within + df between 3. Calculate Variance (MS) - MS btwn= SSbtw/dfbtwn - MS within= SSwithin/ df within 4. Calculate F obtained - Fobt= MSbtwn/MSwithin 5. Evaluate Fobt with Fcrit L> fcrit is found via.... Df btwn= numerator, df within= denominator ..... and alpha on table F. 6. Construct an ANOVA Summary Table
Layout of an Anova Summary Table?
Source SS Df MS Fobt Fcrit
Btwn —- — — — —
Within —- — — — —
Total —- —
On the ANOVA summary table how is significance shown?
- by the Fobt that is sig
If we decide we should reject Ho we have determined that the IV is having an effect on the DV. What is the next step?
- determine the size of the effect that the IV is having on the DV.
L> Omega Squared is a method to do this
What is the formula for omega squared?
SStotal + MSwithin
What is the criteria from Cohen to interpret effect size?
0.01-0.05 =small effect
0.06-0.13= medium effect
>0.14 = large effect
If you had an omega squared value of 0.742 what does this mean? (2)
- it means that the UV accounts for 74.2% of the variability in the DV. It also means that something else (unknown) accounts for 25.8% of the variability in the DV.
What is another method for determining effect size?
Eta Squared
Eta squared is similar or not similar to omega squared.
similar