Statistics How To

Design of Experiments > Experimental Group What is an Experimental Group? An experimental group, also called a treatment group, is a group that receives a specific treatment in an experiment. The “group” consists of test subjects, such as people, animals, cells, or plats, while the “treatment” refers to the variable being studied. For instance, a … Read more

Probability Distributions > Cramp function distribution Cramp Function Distribution Definition The (complex) cramp function distribution, also called the error function, is a continuous probability distribution defined as [1]: The first equality in the formula states that the error function can be expressed as the integral of the Gaussian (normal) function from 0 to x. The … Read more

< Probability Distributions < Bathtub-Shaped Distribution What is a Bathtub-Shaped Distribution? The bathtub-shaped distribution is used in survival analysis and reliability engineering to describe a product or system’s’s failure rate over its lifespan. The term “bathtub” comes from the shape of the hazard function when plotted over time. The distribution is high at the beginning, … Read more

Types of Functions < Loss function What is a Loss Function?   A loss function is a way to measure how far off a prediction or decision is from the true value or outcome.  Its purpose is to give us a way to optimize model parameters to improve accuracy. Different types of loss functions exist … Read more

Statistics Definitions > Risk Function (Statistics) What is a Risk Function? In statistical decision theory, the risk function is the expected value of a loss function. Risk functions are used to evaluate the performance of estimators and decision rules — functions or mappings that take observed data as input and output a decision or action.  The … Read more

Statistics Definitions > Multicollinearity Contents: What is Multicollinearity? What Causes Multicollinearity? What Happens to Analyses Detecting Multicollinearity Fixing Detected Multicollinearity What is Multicollinearity?   Multicollinearity occurs when two or more predictor variables in a regression model are highly correlated with each other. In other words, one predictor variable can be used to predict another with … Read more

Statistics Definitions > Population in Statistics What is a Population in Statistics? A population in statistics is a whole group of people or objects from which samples are taken. It is the entire group that we are interested in, and it includes all of the members of the group [1]. A population is the opposite … Read more

Descriptive Statistics > Measures of Spread What are Measures of Spread? Measures of spread (also called measures of dispersion) tell you something about how wide the set of data is. There are several basic measures of spread used in statistics. The most common are: The range (including the interquartile range and the interdecile range), The … Read more

Statistics Definitions < Weighted Sum What is a Weighted Sum? A weighted sum  accounts for the relative importance or influence of individual data points. While a simple summation has each data point contribute equally, a weighted sum assigns a specific weight to each value, giving certain data points more “weight”. A weighted sum is calculated … Read more

< Statistics Definitions < Parzen window estimation What is Parzen Window Estimation? Parzen window estimation (PWE), also called kernel density estimation (KDE), is a non-parametric technique used to estimate a random variable’s probability density function (pdf). It is named after Emanuel Parzen, who developed the method. Unlike parametric estimation methods, non-parametric estimation methods such as … Read more