Observational data were collected by researchers on 189 consecutive births at Baystate MedicalCenter in Springfield, Massachusetts (USA) . The researchers were interested in using logisticregression to identify maternal and other factors associated with the low birth weight births (asper the World Health Organization's definition of low birth weight as < 2500 grams). Theaverage birth weight for the 189 infants in the sample was 2,945 grams (s= 729, range -709-4,990 grams) with 59 infants (30%) meeting the low birth weight criteria.

The first regression relates the log (ln) odds of low birth weight (LBW) to mother's smokingstatus during pregnancy, and is as follows:

, where x

1

= 1 if the mother smoked during pregnancy (and 0if not). The estimated standard error of the slope of x

1

(

) is 0.32.