Describing the spread of data IBMJ 2010; 340 doi: https://doi.org/10.1136/bmj.c1116 (Published 04 March 2010) Cite this as: BMJ 2010;340:c1116
- Philip Sedgwick, senior lecturer in medical statistics
- 1Centre for Medical and Healthcare Education, St George’s, University of London, London SW17 0RE
Using a prospective cohort study design, researchers investigated the relation between slow walking speed and risk of death in older people.1 A sample of 3208 French men and women aged over 65 years living in the community were recruited in 1999. At baseline the sample had a mean age of 73.2 years with a standard deviation of 4.6 years.
Which of the following, if any, are true?
a) The mean age of the sample is a point estimate of the mean age of the population
b) The sample standard deviation is a measure of the spread of …