Analysis of covariance (ANCOVA).

Abstract This chapter deals with analysis of covariance or ANCOVA, a combination of ANOVA and regression. It tests the effects of a mix of continuous and categorical variables on a continuous response variable. Two examples are presented. Example 1 is based on a study investigating the effects of two types of tagging (acrylic paint and subcutaneous microtags) on the growth of the coral reef goby, Coryphopterus glaucofraenum, in the British Virgin Islands and included initial size as a continuous explanatory variable. Example 2 analyses data from a study on the number of pollinaria removed by pollinators from inflorescences of two Sirindhornia orchid species (S. monophylla and S. mirabillis) in relation to the number of flowers in the inflorescence (also count data) and the orchid species (categorical).