The data shown in the following table were collected as part of a study in which the subjects were preterm infants with low birth weights born in three different hospitals. Use dummy variable coding and multiple regression techniques to analyze these data. May we conclude that the three sample hospital populations differ with respect to mean birth weight when gestational age is taken into account? May we conclude that there is interaction between hospital of birth and gestational age?

Plot the original data and the fitted regression equations.

Birth Gestation Hospital Birth Gestation Hospital Weight (kg) Age (weeks) of Birth Weight (kg) Age (weeks) of Birth 1.4 30 A 1.0 29 C

.9 27 B 1.4 33 C 1.2 33 A .9 28 A 1.1 29 C 1.0 28 C 1.3 35 A 1.9 36 B

.8 27 B 1.3 29 B 1.0 32 A 1.7 35 C

.7 26 A 1.0 30 A 1.2 30 C .9 28 A

.8 28 A 1.0 31 A 1.5 32 B 1.6 31 B 1.3 31 A 1.6 33 B 1.4 32 C 1.7 34 B 1.5 33 B 1.6 35 C 1.0 27 A 1.2 28 A 1.8 35 B 1.5 30 B Birth Gestation Hospital Birth Gestation Hospital Weight (kg) Age (weeks) of Birth Weight (kg) Age (weeks) of Birth 1.4 36 C 1.8 34 B 1.2 34 A 1.5 34 C 1.1 28 B 1.2 30 A 1.2 30 B 1.2 32 C