The normal range for infants to take their first independent steps is between

Adoption studies estimate the genetic contribution to a given trait by studying

A) adopted children only. B) adopted children and their biological family. C) adopted children, their biological family, and their adoptive parents. D) none of the above.

In the general linear model, errors in predictions are caused by

A) influences of measured predictor variables. B) influences not measured by any of the predictor variables. C) some fixed influence that is the same for all individuals. D) correlations among the predictor variables.