Introductory Biostatistics

Chapter 8

8.1 (b)bb^ 0 ¼ 0 :0301,bb^ 1 ¼ 1 :1386,yy^¼ 0 :596;(c)t¼ 5 :622,p¼ 0 :0049;(d)

r^2 ¼ 0 :888.

8.2 (b) bb^ 0 ¼ 6 :08, bb^ 1 ¼ 0 :35, ^yy¼ 27 :08; (c) t¼ 2 :173, p¼ 0 :082; (d)

r^2 ¼ 0 :115.

8.3 (b)bb^ 0 ¼ 311 :45,bb^ 1 ¼
 0 :08,^yy¼ 79 :45;(c)t¼
 5 :648,p¼ 0 :0001;(d)

r^2 ¼ 0 :618.

8.4 (a)F¼16.2, df¼(2.19),p¼ 0 :0001;(b)r^2 ¼ 0 :631.

(c)Term bb^ SEðbb^Þ tStatistic pValue

x(food) 
0.007 0.091 
0.082 0.936

x^2 
0.00001 0.00001 
0.811 0.427

8.5 For men: (b) bb^ 0 ¼
 22 :057, bb^ 1 ¼ 0 :538, ^yy¼ 64 :09; (c) t¼ 1 :697,

p¼ 0 :1282;(d)r^2 ¼ 0 :265.

For women:(b) bb^ 0 ¼
 61 :624,bb^ 1 ¼ 0 :715, ^yy¼ 52 :78;(c) t¼ 2 :917,

p¼ 0 :0194;(d)r^2 ¼ 0 :516;(e)relationship is stronger and statistically

significant for women but not so for men.

8.6 (a)Term bb^ SEðbb^Þ tStatistic pValue

Sex 
39.573 81.462 
0.486 0.634

Height 0.361 0.650 0.555 0.587

Sex-by-height 0.177 0.492 0.360 0.724

(b) No ðp¼ 0 : 724 Þ; (c) F¼ 22 :39, df¼ð 3 ; 16 Þ, p¼0.0001; (d)

r^2 ¼ 0 :808.

8.7 For standard: (b) bb^ 0 ¼ 0 :292, bb^ 1 ¼ 0 :362, ^yy¼ 1 :959; (c) t¼ 7 :809,

p¼ 0 :0001;(d)r^2 ¼ 0 :884.

For test:(b)bb^ 0 ¼ 0 :283,bb^ 1 ¼ 0 :280,yy^¼ 1 :919;(c)t¼ 9 :152,p¼ 0 :0001;

(d)r^2 ¼ 0 :913;(e)no indication of e¤ect modification.

8.8 (a)Term bb^ SEðbb^Þ tStatistic pValue

Preparation 
0.009 0.005 
1.680 0.112

Log(dose) 0.443 0.088 5.051 <0.001

Prep-by-log(dose) 
0.081 0.056 
1.458 0.164

(b) No, weak indication ðp¼ 0 : 164 Þ; (c) F¼46.23, df¼ð 3 ; 16 Þ,

p¼0.0001;(d)R^2 ¼ 0 :897.

8.9 For AG positive:(b)bb^ 0 ¼ 4 :810,bb^ 1 ¼
 0 :818,^yy¼ 19 :58;(c)t¼
 3 :821,

p¼ 0 :002;(d)r^2 ¼ 0 :493.

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