GATE 2020 BM – Question 57
Recorded pairs (age in years,diastolic BP in mmHg) are (23,65),(24,60),(25,62),(26,70),(28,70),(29,73),(31,75),(35,83),(40,90). Using linear regression, predict diastolic pressure at age 38, to two decimals.
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Correct answer: 86.5 to 87.7
Explanation
Fit y=a+bx by least squares with age as predictor. The sums are n=9,Σx=261,Σy=648,Σx²=7817,Σxy=19212. Thus b=[9×19212−261×648]/[9×7817−261²]=1.693548 and a=72−29b=22.887097. At age thirty-eight, prediction is a+38b=87.241935 mmHg, rounded to 87.24.