Question

breastfeeding burns up to 500 calories per day, so does that mean that women who breastfeed their infants will lose more weight than women who formula feed their infants? a group of researchers studied the amount of weight lost after giving birth by mothers who breastfed their infants and mothers who chose formula feeding. they randomly chose 29 breastfeeding mothers and 21 formula feeding mothers. the researchers recorded how much weight each group lost at 12 months after childbirth. the amount of weight lost was found to be normally distributed. the difference in the mean amount of weight lost for the two samples (breastfeeding vs. formula feeding) is 2.0 kg and the 95% confidence interval is (1.05, 4.19). which statement gives the best interpretation of what we can conclude about the impact of breastfeeding on the amount of weight lost after childbirth? a. there is a 95% chance that if a woman breastfeeds her baby that she will lose an extra 1.05 kg to 4.19 kg than if she used formula to feed her baby. b. when breastfeeding mothers are compared to formula feeding mothers, we are 95% confident that the mean amount of weight lost 12 months after childbirth is between 1.05 kg and 4.19kg more than the mean amount of weight lost by formula feeding mothers. c. this study does not suggest that there is a difference in mean amount of weight lost after childbirth when we compare breastfeeding mothers to formula feeding mothers. d. we are 95% confident that on average, breastfeeding causes an extra weight loss of 1.05 kg to 4.19 kg.

Explanation:

• A confidence interval for the difference in means gives a range of values within which the true difference in population means is likely to lie.
• Option A is incorrect because a confidence interval is about the population means, not an individual woman.
• Option C is incorrect as the confidence interval does not contain \(0\) (since \(1.05>0\)), so it does suggest a difference.
• Option D is incorrect because we cannot say breastfeeding “causes” weight loss from an observational study (this is an association, not causation).
• Option B is correct as it correctly interprets the confidence interval in terms of the difference in mean weight loss between the two groups (breast - feeding and formula - feeding mothers).

Answer:

B. When breastfeeding mothers are compared to formula feeding mothers, we are 95% confident that the mean amount of weight lost 12 months after childbirth is between 1.05 kg and 4.19kg more than the mean amount of weight lost by formula feeding mothers.