To determine whether breast feeding causes bone mineral loss in nursing mothers.
Data from a study by Laskey et al. (1998) represented percent change in mineral content of women's spines over three months. Group 2 were women who had breast fed their infants (n2 = 47). Group 1 was women of similar age who where neither pregnant nor lactating (n1 = 22). [Comment: Group numbering is opposite from what I expected because I used the .xls data supplied by the textbook publisher to aid in the analysis: group 1 was the "control group" in their spreadsheet.]
Dr. G. supplied the first page of the published article by way of background (personal communication, 2/24/05). Data are found on p. 49 of our textbook (Moore, 2003).
Side-by-side stemplots were used to organize and explore the data. Stemplots are described in Chapter 1 of our text. Dr. G. discussed the side-by-side modification of the stemplot on 2/22/05. Means and standard deviations were calculated in the usual manner, as were five-number summaries (Moore, 2004, Chapter 2). Histograms were produced with SPSS version 11.
Side-by-side stemplot
Controls Breast-feeding women
|-8|3
|-7|08
|-6|25588
|-5|12233679
|-4|0347799
|-3|01368
2|-2|011223557
65|-1|008
11124446|-0|38
0379| 0|234
0127| 1|7
249| 2|2
(x 1)
Percent change in mineral content
Means, standard deviations, 5-point summary
| Statistics | Other women (controls) | Breast-feeding women |
| mean | 0.309 | -3.587 |
| standard deviation | 1.2983 | 2.5056 |
| 5-point summary | -2.2, -0.4,-0.05, 1.125, 2.9 | -8.3, -5.3, -3.8, -2.1. 2.2 |
| Histograms | |
|
To be discussed in class . . .
Laskey, M. A., Prentice, A., Hanratty, L. A., Jarjou, L. M. A., Dibba, B., Beavan, S. R., & Cole, T. J. (1998). American Journal of Clinical Nutrition, 67, 685 - 692.
Moore, D. S. (2003). The Basic Practice of Statistics (3rd ed.). New York: Freeman.
