Endgames Statistical Question

Simple linear regression

BMJ 2013; 346 doi: https://doi.org/10.1136/bmj.f2340 (Published 12 April 2013) Cite this as: BMJ 2013;346:f2340
1. Philip Sedgwick, reader in medical statistics and medical education
1. 1Centre for Medical and Healthcare Education, St George’s, University of London, Tooting, London, UK
1. p.sedgwick{at}sgul.ac.uk

Researchers investigated the association of right ventricular size and function with varying degrees of pulmonary hypertension. A cross sectional study design was used. Participants were 190 patients referred to a pulmonary hypertension clinic.1

Measurements of right ventricular size included right ventricular end systolic area (RVESA) recorded echocardiographically. The extent of pulmonary hypertension was indicated by pulmonary artery systolic pressure (PASP). A scatter plot of pulmonary artery systolic pressure against right ventricular end systolic area was presented (figure). Linear regression analysis was used to examine the association between right ventricular size and degree of pulmonary hypertension. The resulting fitted linear regression line was given by PASP=2.7133RVESA+15.717.

Scatter plot of pulmonary artery systolic pressure (PASP) against right ventricular end systolic area (RVESA)

Which of the following statements, if any, are true for the linear regression line?

• a) Pulmonary artery systolic pressure can be predicted given a value of right ventricular end systolic area

• b) Right ventricular end systolic area can be predicted given a value of pulmonary artery systolic pressure

• c) It was assumed that the variation in pulmonary artery systolic pressure was equal for all values of right ventricular end systolic area

• d) The line can be extrapolated outside the observed range of values for right ventricular end systolic area

Statements a and c are true, whereas b and d are false.

The researchers investigated the association …

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