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# 8.2.2.2. Interaction statistical analysis

An analysis of variance is performed at each time, using a variance error which is computed from both the variance error of the main ANOVA described previously in the table (hives within group, [R x hives] within groups). This computation is performed for comparisons between groups. This combined mean square error with pq(n-1) = 50 degrees of freedom is 0.0766. This degree of freedom must be corrected because this common error comes from two sources of heterogeneity. This correction from SATTERTHWAITE gives the degree of freedom of 43 instead of 50 theoretical degrees.

All kinds of comparisons between both groups will be performed with the same common variance error.

-   The comparisons at each level (time of measure) give the statistical results:
-   3 days after exposure:               (MS=0.4408; F=5.75, observed probability p=0.0209).
-   7 days after exposure:      (MS=1.6875; F=22.03, observed probability p<0.0001).
-   14 days after exposure:    (MS=0.4408; F=5.75, observed probability p=0.0209).
-   19 days after exposure:    (MS=0.7500; F=9.79, observed probability p=0.0031).
-   7 days after exposure, the comparison between means conduct to reject the null hypothesis with a probability
< 0.0001. This observed probability is between 0.01 and 0.05 after 3 days and 14 days. 19 days after exposure,
this observed probability is between 0.001 and 0.01.

All the statistical conditions for this statistical model are assumed to be obtained.