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Question 1

ANCOVA?

Answer 1

Analysis of covariance. It is useful when comparing many slopes since it can simultaneously test 3 null hypotheses.

H_0: area has no effect on the # of species

H_0: Islands and mainland areas are the same for mean number of species. (whether the lines are shifted from the others)

H_0: area and island/mainland type do not interact in determining the # of species. (Is the slope if one line significantly differ than the other).

     H_0 = beta_1 = beta_2 = beta_3 ….

H_A = at least one of the slopes is different from the others.

Question 2

Logistic regression?

Answer 2

Tests for relationship between a numerical variable (as the explanatory variable) and a binary variable (as the response).

E.g., does the dose of a toxin affect the probability of survival?

Does the length of a peacock’s tail affect its probability of getting a mate?