 # Statistics How To

## Omnibus Test

Hypothesis Testing > An omnibus test (also called a combined test) is an overall test for a whole group of results. For example, an ANOVA is an omnibus test – if you reject the null hypothesis, then one pair may…

## Contrast Analysis

Hypothesis Testing > Contrast analysis is a way to provide more precise conclusions than a traditional analysis of variance for tests with factorial designs. While an F-Test will give you an idea of whether your independent variables have an effect…

## Sample Space Examples and The Counting Principle

Probability and Statistics > Probability > Sample Space Examples Contents: What is a Sample Space? Large Sample Spaces The Counting Principle Continuous Sample Spaces What is a Sample Space? The sample space of an experiment is all possible outcomes for…

## NRMSE

Statistics Definitions > The normalized root mean squared error (NRMSE), also called a scatter index, is a statistical error indicator defined as . Where Oi are observed values and Si are simulated values. It can also be calculated as RMSE/range…

## Test Statistic: Definition, Types of Test Statistic

Statistics Definitions > Test Statistic A test statistic is used in a hypothesis test when you are deciding to support or reject the null hypothesis. The test statistic takes your data from an experiment or survey and compares your results…

## Euler Diagram: How to Draw one in Easy Steps

Probability and Statistics > Probability > How to Create an Euler Diagram Euler diagram: Overview An Euler diagram is similar to a Venn diagram. While both use circles to create diagrams, there’s a major difference: Venn diagrams represent an entire…

## X-MR (X-Moving Range) Chart

Descriptive Statistics: Charts and Graphs > The X-MR Chart (X-Moving Range Chart) is a control chart used in process monitoring. While the X-only chart plots processes with individual observations, the X-MR plots a combination of individual measurements and a moving…

## Bias in Statistics: Definition, Selection Bias & Survivorship Bias

Probability and Statistics > Basic Statistics > What is Bias in Statistics? What is Bias in Statistics? Biased Estimators. What is Selection Bias in Statistics? Ideally, you should randomly select every participant in a survey. But, sometimes biases creep in,…

## Clopper-Pearson Exact Method

Confidence Intervals > Clopper-Pearson The Clopper-Pearson interval, also called the exact interval is an alternative to calculating binomial confidence intervals using normal approximation. It is based on inverting the equal-tailed binomial tests. It is the most commonly cited exact method…

## Mean Absolute Percentage Error (MAPE)

Statistics Definitions > The mean absolute percentage error (MAPE) – also called the mean absolute percentage deviation (MAPD) – measures accuracy of a forecast system. It measures this accuracy as a percentage, and can be calculated as the average absolute…