Statistics Definitions > What is the Ceiling Effect? A ceiling effect happens when your questionnaire or test components/problems aren’t hard enough; An artificially low ceiling is created that is easy to achieve. If it exists in your test or survey,…

## Error Bar: Definition

Statistics Definitions > What is an Error Bar? An error bar is a (usually T-shaped) bar on a graph that shows how much error is built in to the chart. The “error” here isn’t a mistake, but rather a range…

## Directional Test

Hypothesis Testing > A directional test is a hypothesis test where a direction is specified (e.g. above or below a certain threshold). For example you might be interested in whether a hypothesized mean is greater than a certain number (you’re…

## Confusion Matrix

Matrices > A confusion matrix, in predictive analytics, is a two-by-two table that tells us the rate of false positives, false negatives, true positives and true negatives for a test or predictor. We can make a confusion matrix if we…

## Practical Significance

Statistics Definitions > Practical Significance Practical significance relates to whether a result from a statistical hypothesis test is useful in real life. It is a way to address some of the limitations with traditional testing and answers the question Do…

## V Statistics

Statistics Definitions > The term “V statistic” could refer any one of several statistics. Which one you’re using depends on what type of analysis you’re performing. For example: Correlation analysis: Cramer’s V Discriminant analysis: Rao’s V MANOVA: Pillai’s V These…

## Test of Association

Statistics Definitions > When you hear the term Test of Association in statistics, it usually means the Chi-Square Test. However, it’s used in an informal sense to mean many things. Loosely speaking, any time you’re trying to find out if…

## Inductive Statistics

Statistics Definitions > Inductive statistics (or inductive reasoning) is a branch of statistics that deals with taking samples from a larger population and using that data to: Draw conclusions, Make decisions, Forecast, Predict future behavior. For example, you might want…

## Weak Instrument: Definition

Regression Analysis > Weak instruments can wreak havoc with your regression analysis. “Instruments” (instrumental variables) are a third variable, Z, used when you have endogenous variables—variables that are influenced by other variables in the model. Instruments are used to account…

## Confounding by Indication

Confounding > A medication’s indication can act as a confounder in observational studies, especially when the drug’s effectiveness is being assessed (Ahrens & Pigeot, 2007). Indication refers to how a particular drug is used for treatment of a certain disease.…