Lecture 8 Homework
(22 points) Newborn babies normally lose between 5% to 7% of their weight in the
first week of life. For proper development, it is important to ensure babies quickly
gain weight after the initial weight loss. Two leading manufacturers of baby-food
are Infamil and Similac. Similac recently came up with a new baby formula and
claims that it allows babies to gain weight faster than Infamil’s formula. To test
this claim, a pediatrician at Riverside Health Care facility decides to track weight
gain between week 1 and week 4 of life for a sample of babies fed with Similac
and for a different sample of babies fed with Infamil formulas. The weight gains
(in ounces) are recorded in the file “baby_food.csv”.
Comparing two populations-> interval data -> central location-> Independent
samples -> Test normality of both populations-> if normal -> T test and
estimator of the difference of the means for independent samples
Babies are fed similac or infamil, but not both. Because its measuring one baby
taking one of those medicines, not the same baby taking both. One does not
affect another.
a. (2 points) What are the point estimates of the average weight gains for
babies fed with Infamil and for babies fed with Similac?
Xinfamil = 33.41463
Xsimilac = 35.29268
b. (1 points) Does it appear that feeding babies with Similac’s formula leads to
a higher weight gain? Briefly explain why or why not.
Yes, it appears that babies gain more weight with similac (35.29268 ounces)
versus Infamil (33.41463 ounces). This result is based on descriptive
statistics.
c. (6 points) Test both samples for normality. (a) Identify the hypotheses to be
tested, (b) Report p-values for Shapiro-Wilk tests for both samples and (c)
state your conclusion as to whether the samples are normally distributed or
not.
H0: data = normal
H1: data /=/ normal
Infamil p-value= 0.4889 (vs. 0.05) fail to reject. Data is normal
Similac p-value = 0.6677 Fail to reject. Data is normal
