One study measured wrist bone density (unit g / cm2) Men and women aged 50-75

(n = 800). Subjects were randomly selected. Bone density (BMD) was modeled by linear regression,

which were explained by Age and Gender. Below is the R-printout of that material.

> head (bmddat) BMD Age Gender 1 0. 3923660 66 Female 2 0. 4635478 54 Male 3 0. 6579392 50 Male 4 0.3142545 74 Male 5 0. 4966346 59 Male 6 0. 2436903 53 Female > summary (bmddat) BMD Age Gender Min. :0. 1006 Min. :50.00 Length : 774 ist Qu. :0.2764 1st Qu. :56.00 Class : character Median :0.3671 Median :62.00 Mode : character Mean :0. 3658 Mean : 62 . 46 3rd Qu. : 0. 4501 3rd Qu. :69.00 Max. :0.7818 Max. :75.00 > mi summary (m1) Call : Im (formula = BMD - I(Age - 50) + factor (Gender), data = baddat) Residuals : Min 1Q Median 3Q Max -0.26510 -0.06344 -0. 00226 0.06326 0.34220 Coefficients : Estimate Std. Error t value Pr(>|t|) (Intercept) 0. 3746540 0. 0076665 48. 87