(d) (7 pts) Independence of measurements across andwithin groups: trees were sampled randomly, andwere experimentally chosen to be burnt and in-vaded by beetles.It can be pointed out that iftrees are located in regions that are far apart, thenthe region might affect the genetic backgroundor the presence/absence of beetles and raise con-cerns about this independence assumption. Butthis assumption seems to be met from the avail-able information.Normality of measurements within each group:Having a qq-plot of residuals would make it easyto see, but the dotplots show no outlier, no appar-ent skew, and makes us think normality probablyholds here.Equal variances:seems okay.Sample standarddeviations are quite similar (the largest is no largerthan twice the smallest). Furthermore, Levene’stest supports this assumption:F= 0.21 on 3and 34 df givesp >0.25 and leads us to acceptσ1=σ2=σ3=σ4.Frequency204060801000102030Summary of grades●●●●●●●●6877882
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