Question

One of the best indicators of the health of a baby is his/her weight at birth. In the United States, mothers who live in poverty generally have babies with lower birthweight than those who do not live in poverty, the average birthweight for women living in poverty is 2800 grams. Recently, a local hospital introduced an innovative new prenatal care program to reduce the number of low birthweight babies born in the hospital. In the first year, 25 mothers, all of whom live in poverty, participated in this program. Data drawn from hospital records reveals that the babies born to these women had a birthweight of 3075 grams, with a standard deviation of 500 grams. Perform a hypothesis test to determine if birthweight for women receiving the new prenatal care program is significantly different from birthweight for women living in poverty. Please follow the four steps and compute the effect size (cohen’s d), and please interpret the results.

a) a. t=2.75, 2.75>2.064, failed to reject null. Cohen’s d = 0.85, large effect.

b) b. t=2.75, 2.75>2.064, reject null. Cohen’s d = 0.55, medium effect.

c) . z=2.75, 2.75>2.064, reject null. Cohen’s d = 0.55, medium effect

d). z=2.75, 2.75>2.064, reject null. Cohen’s d = 0.85, large effect.

Answer 1

Cohen's d =|3075-2800|/500 =0.55

hence option B is correct:  t=2.75, 2.75>2.064, reject null. Cohen’s d = 0.55, medium effect.