The following data were collected on a simple random sample of 20 patients with hypertension. The variables are Y ¼ mean arterial blood pressure mm Hg ð Þ

X1 ¼ age years ð Þ

X2 ¼ weight kg ð Þ

X3 ¼ body surface area sq m ð Þ

X4 ¼ duration of hypertension years ð Þ

X5 ¼ basal pulse beatsthn ð Þ =min X6 ¼ measure of stress Patient Y X1 X2 X3 X4 X5 X6 1 105 47 85.4 1.75 5.1 63 33 2 115 49 94.2 2.10 3.8 70 14 3 116 49 95.3 1.98 8.2 72 10 4 117 50 94.7 2.01 5.8 73 99 5 112 51 89.4 1.89 7.0 72 95 6 121 48 99.5 2.25 9.3 71 10 7 121 49 99.8 2.25 2.5 69 42 8 110 47 90.9 1.90 6.2 66 8 9 110 49 89.2 1.83 7.1 69 62 10 114 48 92.7 2.07 5.6 64 35 11 114 47 94.4 2.07 5.3 74 90 12 115 49 94.1 1.98 5.6 71 21 13 114 50 91.6 2.05 10.2 68 47 14 106 45 87.1 1.92 5.6 67 80 15 125 52 101.3 2.19 10.0 76 98 16 114 46 94.5 1.98 7.4 69 95 17 106 46 87.0 1.87 3.6 62 18 18 113 46 94.5 1.90 4.3 70 12 19 110 48 90.5 1.88 9.0 71 99 20 122 56 95.7 2.09 7.0 75 99