Statistics How To

Find Outliers > Dixon’s Q Test What is Dixon’s Q Test? Dixon’s Q test, or just the “Q Test” is a way to find outliers in very small, normally distributed, data sets. Small data sets are usually defined as somewhere between 3 and 7 items. It’s commonly used in chemistry, where data sets sometimes include … Read more

Statistics Definitions > Chauvenet’s Criterion What is Chauvenet’s Criterion? Chauvenet’s criterion is a way to identify outliers. The method works by creating an acceptable band of data around the mean, specifying any values that fall outside that band should be eliminated. The formula to calculate the band is: Where n is the sample size. Normal … Read more

Statistics Definitions > Goldfeld Quandt Test What is the Goldfeld Quandt Test? The Goldfeld Quandt Test is a test used in regression analysis to test for homoscedasticity. It compares variances of two subgroups; one set of high values and one set of low values. If the variances differ, the test rejects the null hypothesis that … Read more

Statistics Definitions > Park Test What is the Park Test? The Park Test is a test for heteroscedasticity. Heteroscedasticity means that the variances of the errors are not the same across a set of independent (predictor) variables. Use the Park test for heteroscedasticity if you have some variable Z that you think might explain the … Read more

Regression Analysis > Quadratic Regression Contents (Click to skip to that section): What is Quadratic Regression? The Quadratic Equation R-Squared Find the Equation with a Calculator Find by Hand What is Quadratic Regression? Quadratic regression is finding the best fit equation for a set of data shaped like a parabola. The first step in regression … Read more

Design of Experiments > Generalizability and Transferability in Statistics and Research What are Generalizability and Transferability? Generalizability and Transferability are two related terms used in research. Generalizability is a measure of how well a researcher thinks their experimental results from a sample can be extended to the population as a whole. It is usually used … Read more

Statistics Definitions > Permuted Block Randomization What is Permuted Block Randomization Permuted block randomization is a way to randomly allocate a participant to a treatment group, while maintaining a balance across treatment groups. Each “block” has a specified number of randomly ordered treatment assignments. For example, let’s you had treatment groups A and B, and … Read more

Sampling > Stratified Randomization in Clinical Trials You may want to read this article first: Permuted Block Randomization What is Stratified Randomization? In stratified randomization (sometimes called Stratified Permuted Block Randomization), trial participants are subdivided into strata, then permuted block randomization is used for each stratum. The goal is to create a balance of clinical/prognostic … Read more

RCTs > Allocation Concealment What is Allocation Concealment? Allocation concealment is a when the person (or system) responsible for allocating people to different treatment groups and control groups: Doesn’t know what the next treatment allocation will be and Conceals the results of the allocation from others. Allocation concealment is different from blinding. With blinding, the … Read more

Bias in Statistics > Ascertainment Bias What is Ascertainment Bias? Ascertainment bias happens when the results of your study are skewed due to factors you didn’t account for, like a researcher’s knowledge of which patients are getting which treatments in clinical trials or poor Data Collection Methods that lead to non-representative samples. Clinical Trials Ascertainment … Read more