A developmental psychologist investigates the effect of mothers’ carrying behavior on infant sleep patterns. Specifically, the investigator solicits help from 40 mothers of newborns. The psychologist...

A developmental psychologist investigates the effect of mothers’ carrying behavior on infant sleep patterns. Specifically, the investigator solicits help from 40 mothers of newborns. The psychologist trains 20 mothers in a carrying method that presses the newborn’s head against the mother’s breast; the other 20 mothers are not instructed in a particular carrying method. All mothers are trained to record the number of hours their newborn sleeps each 24-hour period. Records are kept for 3 months in both groups. The mean 24-hour sleep period for infants in the instructed group was 12.6 (SD 5.1); in the uninstructed group the mean was 10.1 (SD 6.3).

A Calculate the 95% confidence interval for the difference between the two means.

B What may be said about the effect of training based on an examination of the confidence interval for this experiment?

C What is the effect size for this experiment? Interpret the effect size measure based on Cohen’s guide lines for small, medium, and large effects.