[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Epidemiology](https://durgical.com/en/epidemiology/) › Biostatistics # Biostatistics Data and distributions, hypothesis testing, p values, confidence intervals, power, sample size and statistical tests. 24 pages ## Statistical test - [**Analysis of variance (ANOVA)** It compares the means of three or more groups at once, in a single test, without inflating the…](https://durgical.com/en/epidemiology/analysis-of-variance/) - [**Chi-square test** It compares proportions between groups by measuring how far the observed counts are from those…](https://durgical.com/en/epidemiology/chi-square-test/) - [**Linear regression** It fits a straight line that predicts one numerical variable from another](https://durgical.com/en/epidemiology/linear-regression/) - [**Logistic regression** It models a yes-or-no outcome from several variables and gives odds ratios (OR) adjusted for the…](https://durgical.com/en/epidemiology/logistic-regression/) - [**McNemar test** It compares two proportions measured in the same people (before and after) or in matched pairs](https://durgical.com/en/epidemiology/mcnemar-test/) - [**Non-parametric tests** Tests that compare groups using the order of the data (ranks) instead of their values, useful…](https://durgical.com/en/epidemiology/non-parametric-tests/) - [**Student's t test** It compares two means and says whether the gap between them is larger than chance would explain](https://durgical.com/en/epidemiology/student-s-t-test/) ## Concept - [**Choosing a statistical test** The test is chosen with four questions: what type of outcome, how many groups, independent or…](https://durgical.com/en/epidemiology/choosing-a-statistical-test/) - [**Hypothesis testing** Start by assuming there is no difference, then check whether the data would be rare enough under…](https://durgical.com/en/epidemiology/hypothesis-testing/) - [**Multiple comparisons** The more tests are run, the easier it is for one to come out significant by chance alone](https://durgical.com/en/epidemiology/multiple-comparisons/) - [**Non-response, losses and missing data** When some participants' data are missing, the result can shift](https://durgical.com/en/epidemiology/non-response-losses-and-missing-data/) - [**Normal distribution** The bell curve: symmetric, with mean, median and mode equal, and fixed shares of the data within…](https://durgical.com/en/epidemiology/normal-distribution/) - [**P value** The p value says how surprising the data would be if there really were no difference](https://durgical.com/en/epidemiology/p-value/) - [**Sample size** How many people are needed to detect the effect that matters with the accepted risk of error](https://durgical.com/en/epidemiology/sample-size/) - [**Skewed distributions** When data have a long tail on one side, the mean drifts toward the tail and stops describing the…](https://durgical.com/en/epidemiology/skewed-distributions/) - [**Statistical analysis plan** Writing down, before seeing the data, how they will be cleaned, described and analysed, so the…](https://durgical.com/en/epidemiology/statistical-analysis-plan/) - [**Statistical power** Power is the probability that a study detects an effect that truly exists](https://durgical.com/en/epidemiology/statistical-power/) - [**Statistical vs clinical significance** A statistically significant result does not mean it matters to the patient](https://durgical.com/en/epidemiology/statistical-vs-clinical-significance/) - [**Type I and type II errors** Type I error: seeing a difference that does not exist (false positive)](https://durgical.com/en/epidemiology/type-i-and-type-ii-errors/) - [**Types of variables** Every piece of data has a type: unordered categories, ordered categories, counts or measurements](https://durgical.com/en/epidemiology/types-of-variables/) ## Measure - [**Confidence interval** A range of values for the true value that are compatible with the data](https://durgical.com/en/epidemiology/confidence-interval/) - [**Correlation** It measures how closely two numerical variables rise or fall together, from −1 to +1](https://durgical.com/en/epidemiology/correlation/) - [**Measures of centre and spread** Mean, median and mode tell where the centre of the data lies; range, interquartile range and…](https://durgical.com/en/epidemiology/measures-of-centre-and-spread/) - [**Standard error** The standard error measures how much the mean would vary if the study were repeated on another…](https://durgical.com/en/epidemiology/standard-error/) ## A to Z - [A](https://durgical.com/en/epidemiology/a-z/a/) - [B](https://durgical.com/en/epidemiology/a-z/b/) - [C](https://durgical.com/en/epidemiology/a-z/c/) - [D](https://durgical.com/en/epidemiology/a-z/d/) - [E](https://durgical.com/en/epidemiology/a-z/e/) - [F](https://durgical.com/en/epidemiology/a-z/f/) - [G](https://durgical.com/en/epidemiology/a-z/g/) - [H](https://durgical.com/en/epidemiology/a-z/h/) - [I](https://durgical.com/en/epidemiology/a-z/i/) - [K](https://durgical.com/en/epidemiology/a-z/k/) - [L](https://durgical.com/en/epidemiology/a-z/l/) - [M](https://durgical.com/en/epidemiology/a-z/m/) - [N](https://durgical.com/en/epidemiology/a-z/n/) - [O](https://durgical.com/en/epidemiology/a-z/o/) - [P](https://durgical.com/en/epidemiology/a-z/p/) - [Q](https://durgical.com/en/epidemiology/a-z/q/) - [R](https://durgical.com/en/epidemiology/a-z/r/) - [S](https://durgical.com/en/epidemiology/a-z/s/) - [T](https://durgical.com/en/epidemiology/a-z/t/) - [U](https://durgical.com/en/epidemiology/a-z/u/) - [V](https://durgical.com/en/epidemiology/a-z/v/) - [W](https://durgical.com/en/epidemiology/a-z/w/) - [Y](https://durgical.com/en/epidemiology/a-z/y/) [← Epidemiology, biostatistics and public health](https://durgical.com/en/epidemiology/) Educational content on epidemiological and statistical methods; the examples use made-up numbers to teach the calculation. Not a clinical or legal guide: current Colombian rules are in the official sources. Representative model, for educational purposes only. --- Source: https://durgical.com/en/epidemiology/areas/stats/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/epidemiology/areas/stats/