Statistics How To

Sufficiency > The term “ancillary statistic” is one of those terms that mean something slightly different depending on where you read about it. Most (but not all) authors agree that an ancillary statistic is a distribution constant statistic that can be combined with a maximum likelihood estimator to create a minimally sufficient statistic. The ancillary … Read more

ANOVA > Nested Model Contents: What is a Nested Model? Nested Factors Nested ANOVA Nested vs. Crossed What is a Nested Model? Very simply, “nested” means that one model is a subset of another. For example, take a model for pregnancy outcomes that includes four categorical independent variables: Age, Weight, Pre-existing conditions, Hereditary factors. Several … Read more

Statistics Definitions > Contents: What is a Multiset? What is Multichoose? 1. What is a Multiset? A multiset in mathematics is a generalization of the concept of a set. It’s a collection of unordered numbers (or other elements), where every element x occurs a finite number of times. The difference between sets and multisets is … Read more

Statistics Definitions > A condition index shows the degree of multicolinearity in a regression design matrix. It is an alternative to other methods like variance inflation factors. Although there’s no generally agreed on method to identifying multicollinearity in data, condition indices give a relatively straightforward way to find potential issues. The indices are widely available … Read more

RCTs > In clinical trials, the clinical significance (“treatment effects”) is how well a treatment is working. For example, a drug might be said to have a high clinical significance if it is having a positive, measurable effect on a person’s daily activities. Common measures of clinical significance include relative risk, absolute risk, and number … Read more

Statistics Definitions > A ratio estimator, commonly used in survey sampling, is a ratio of the means of two random variables. They are biased, so corrections for error must be made when using them in experiments. Why Use a Ratio Estimator? A couple of circumstances could lead you to use a ratio estimator instead of … Read more

Statistics Definitions > Triangulation, in statistics and the social sciences, is a research tactic that involves using two or more different ways to verify one result. It takes its name from the triangulation used in land surveys and navigation, where data from two points in space are used to determine a third. It allows us … Read more

Statistics Definitions > The floor effect is what happens when there is an artificial lower limit, below which data levels can’t be measured. Usually, this is because of inherent weaknesses in the measuring devices or the measurement/scoring system. The lower limit, which affects dependent variables, is referred to as the floor, and can badly skew … Read more

Statistics Definitions > A random walk is a sequence of discrete, fixed-length steps in random directions. Random walks may be 1-dimensional, 2-dimensional, or n-dimensional for any n. A random walk can also be confined to a lattice. The Simplest Random Walk: Walking in One Dimension Random walks are simplest when they’re taken in one dimension. … Read more

Correlation Coefficient > Goodman and Kruskal’s lambda coefficient measures the proportional reduction in error in crosstab analysis. The statistic can be symmetric, where you do not have to specify which variable is dependent, and asymmetric where the dependent variable is specified. ε1 is the overall non-modal frequency and ε2 is the sum of the non-modal … Read more