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Manipulative Nested ANOVA
Manipulative experiment- “manipulation”
- laboratories – rigidly controlled- natural system – loosely controlled
Nested Experiments
levels of one factor (A) are NOT the same in each levels of the other factor
The levels of B are different for different levels of A
A
B
• A Nested design is not the same as a two-way ANOVA which is represented by:
Nested ANOVA Models
1. Mixed – fixed main group factor, random subgroup
factor
2. Pure – group and subgroup factors are random
Hypothesis Testing
Ho: µA = µB …. µi (groups have the same means)
Ha: there is a difference in group means
Ho: µA1 = µA2 … µAa (subgroups within each groups have the same means)
Ha: there is a difference in subgroups means
Calculations
ANOVA Table
Fcrit
Example:Two independent measurements (replication level) of
the length of the left wing have been made on 4 female mosquitoes Aedes intrudens (nested factor) reared in each of 3 cages (main factor). The total number of observations is thus 3 x 4 x 2 = 24. The data are the following:
Sokal and Rohlf , 1995
1. Ho: µcage1 = µcage2 = µcage3
Ha: there is a significant difference in the length of left wings of mosquitoes in at least one of the cages
Ho: µmosquito1 = µmsoquito2 = µmosquito3 = µmosquito4
Ha: there is a significant difference in the length of left wings in at least one of the of mosquitoes
Sokal and Rohlf , 1995
Conclusion: Cage factor have no significant effect on the length of left wing in mosquitoes, but there is a variation
Fcrit
4.26
2.80