Statistics How To

Bias > Allocation bias happens when researchers don’t use an appropriate randomization technique, leading to marked, systematic differences between experimental groups and control groups. It can also happen further down the line, if clinical staff don’t follow the procedures set in place by the researchers. One study (Salonen et al, 1992) highlighted a problem with … Read more

Sampling > Resampling techniques are a set of methods to either repeat sampling from a given sample or population, or a way to estimate the precision of a statistic. Although the method sounds daunting, the math involved is relatively simple and only requires a high school level understanding of algebra. Informally, resample can mean something … Read more

Probability Distributions > What is the Lomax Distribution? The Lomax distribution is a heavy tailed distribution originally proposed by Lomax (1987), who used it in his analysis of business failure lifetime data. The distribution, which is basically a shifted Pareto distribution, is widely used in survival analysis, and has many applications in actuarial science, economics, … Read more

Statistics Definitions > Upper Tail and Lower Tail What is a “Tail”? The “tails” of a distribution are, just like the name suggests, the appendages on the side of a distribution. Although it can apply to a set of data, it makes more sense if that data is graphed, because the tails become easily visible. … Read more

Statistics Definitions > What is the Proportional Reduction in Error (PRE Test)? The Proportional Reduction in Error (PRE Test) is a statistical criterion which quantifies the extent that knowledge about one variable can help us predict another variable. That is to say, it helps you understand to what degree knowing a variable x can help … Read more

Statistics Definitions > Varimax rotation is an important second step in Factor Analysis and Principal Component Analysis. The initial factor analysis step has an infinite number of initial, or provisional, factors. Factor rotation, including Varimax rotation, transforms the initial factors into new ones that are easier to interpret. Factor Rotations Factor rotations make the expression … Read more

Regression Analysis > What is Regularized Regression? Regularized regression is a type of regression where the coefficient estimates are constrained to zero. The magnitude (size) of coefficients, as well as the magnitude of the error term, are penalized. Complex models are discouraged, primarily to avoid overfitting. “Regularization” is a way to give a penalty to … Read more

Statistics Definitions > What is Linear Discriminant Analysis? In statistics, pattern recognition and machine learning, linear discriminant analysis (LDA), also called canonical Variate Analysis (CVA), is a way to study differences between objects. This sorting method uses a linear combination of features to characterize classes. More specifically, scores that separate an object from one particular … Read more

Experimental Design > Subgroup analysis is research that focuses on one or more subgroups of the main data set. It attempts to find and illustrate patterns within and between subgroups. The technique is widely used in medical research; The price tag that comes with any clinical trial means that researchers are under pressure to derive … Read more

Statistics Definitions > A quintile is a 1/5th (20 percent) portion of the whole. In statistics, it’s a population or sample divided into five equal groups, according to values of a particular variable. It can also be used to refer to the cut-of points (quartiles) for these portions. 0 – 20% is the first quintile … Read more