Health Dictionary
Reliable, easy-to-read patient information on common medical conditions — written in plain language, free of jargon, and grounded in current evidence. Browse the most frequent diagnoses, understand what they mean for everyday life, and learn which steps and questions help you have a focused conversation with your doctor.
Descriptive statistics
Introduction
Measurements of central tendency
Measurements of central tendency
- Mean In general understanding, the mean is the average. Suppose there are five people. The people have, respectively, 1 TV in their house, 4 TVs, 2 TVs, no TVs and 3 TVs. You would say that the ‘mean’ number of TVs in the house is 2 (1+4+2+0+3)/5=2.
- Median The median is the point at which half are above and half are below. In the above example, the median is also 2, because in this group of 5 people, 2 people have more than 2 TVs in their house and 2 people have fewer than 2 TVs in their house.
Measurements of variation
Measurements of variation
- Standard deviation (SD) is a measure of variation or scatter. The standard deviation does not change with sample size.
- Variance is the square of the standard deviation:
- <math>s^2</math>
- Standard error of the mean (SEM) measures the how accurately you know the mean of a population and is always smaller than the SD.[1] The SEM becomes smaller as the sample size increases. The sample standard devision (S) and SEM are related by:
- <math>SE_\bar{x}\ = \frac{s}{\sqrt{n}}</math>
- 95% confidence interval is + 1.96 * standard error.
- Coefficient of variation (CV) is the ratio of the standard deviation <math>\ \sigma </math> to the mean <math>\ \mu </math>, <math>c_{\rm v} = \frac{\sigma}{\mu}.</math>[2]. “Commonly, a CV of < 5% is deemed acceptable[2].
See also
See also
References
References
- ↑ “What is the difference between “standard deviation” and “standard error of the mean”? Which should I show in tables and graphs?”. Retrieved 2008-09-18.
- ↑ 2.0 2.1 Campbell, Michael J.; Walters, Stephen John; Machin, David (2021). Medical statistics : a textbook for the health sciences. Chichester, West Sussex. ISBN 978-1-119-42364-5. OCLC 1163960928.