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Anova

There are two groups of sucjects A(n=50) and B(n=60).

Each subjects has to test five different concentrations of a solution (5%,10%, 20%, 40%, 80%). When a subject tastes a solution, he gives it a score how he likes it (from 1 to 10).

I need to analyze how the ratings depend on group and solution.
I am using a two-way ANOVA.

What would be the correct df for this problem?

The total df.-- IS it 110-1? But the total number of observations is 5 * 110... stat package gives me total df 554. Did I enter the data wrong?

Also, what if an interaction of the two factors is significant, can I perform any comparisons between different factor/level combinations? If yes, with what test?

Solution Preview

An approach that you may use to analyze your data set is by dividing it up into different categories depending on group an concentrations of a solution, this seems to be the logical way to go about it since you say that you need to analyze how the ratings depend on group and solution. That would mean that, starting with group A, you would conduct the experiment by asking each subject to taste the solution with the 5% concentration and giving it the score out of 10, you would then obtain a data set with group A scores for the solution with the 5% concentration. You would then repeat the experiment with each concentration level (10%,.....,80%) and this would give you 5 data ...

Solution Summary

The solution discusses two groups of sucjects A(n=50) and B(n=60).

Each subjects has to test five different concentrations of a solution (5%,10%, 20%, 40%, 80%). When a subject tastes a solution, he gives it a score how he likes it (from 1 to 10).

I need to analyze how the ratings depend on group and solution.
I am using a two-way ANOVA.

What would be the correct df for this problem?

Also, what if an interaction of the two factors is significant, can I perform any comparisons between different factor/level combinations? If yes, with what test?

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