Statistics How To

Descriptive Statistics > The Bland-Altman plot (also called the Tukey mean difference plot, RA and MA plots, and various other field-specific names) is an XY scatter plot that compares the disagreement, or differences, between two quantitative measurements. It’s similar to correlation, except that correlation measures the relationship between two variables while the Bland-Altman plot measures … Read more

Two Way Tables > Joint Frequency What is Joint Frequency? A joint frequency is how many times a combination of two conditions happens together. For example: Pet owners (condition 1) who are women (condition 2), Democrats (condition 1) who are married (condition 2), Astronauts (condition 1) who are allergic to peanuts (condition 2), Lottery winners … Read more

Bias in Statistics > Funding Bias What is Funding Bias? Funding bias refers to when a study’s outcome is more likely to support the interests of the organization funding the study. A correlation has been found by multiple sources between funding source and outcome of research, for example tobacco research and chemical toxicity studies or … Read more

Probability Distributions > The Landau distribution is a unimodal distribution with a long upper tail; It resembles a normal distribution (called a Gaussian distribution in physics). This distribution has fat tails, which decrease algebraically (as opposed to exponentially) for large values of x. It is defined over the set of real numbers In physics, the … Read more

Statistics Definitions > Estimator What is an Estimator? An estimator is a statistic that estimates some fact about the population. You can also think of an estimator as the rule that creates an estimate. For example, the sample mean(x̄) is an estimator for the population mean, μ. The quantity that is being estimated (i.e. the … Read more

Statistics Definitions > Cramer-Rao Lower Bound What is the Cramer-Rao Lower Bound? The Cramer-Rao Lower Bound (CRLB) gives a lower estimate for the variance of an unbiased estimator. Estimators that are close to the CLRB are more unbiased (i.e. more preferable to use) than estimators further away. The Cramer-Rao Lower bound is theoretical; Sometimes a … Read more

Sampling in Statistics > Efficiency & Efficient Estimator What is Efficiency? The meaning of “efficient” in statistics isn’t much different from the dictionary definition of efficient: “…capable of producing desired results without wasting materials, time, or energy. ~ Miriam Webster. In other words, an efficient procedure produces results that maximize your use of materials, time … Read more

Statistics Definitions > Marginal Mean, Cell Mean What is a Marginal Mean? A marginal mean is (as the name suggests) a mean found in the margins (i.e. the edges) of a contingency table. In other words, it’s the average scores from a group or subgroup in an experiment. The more technical definition is that one … Read more

Probability Distributions > Gompertz Distribution What is the Gompertz Distribution? The Gompertz distribution, named after Benjamin Gompertz, is an exponentially increasing, continuous probability distribution. It’s basically a truncated extreme value distribution (Johnson et. al, 1994). Therefore, it is also called an EVD Type I. Although the theoretical range is from zero to positive infinity, most … Read more

Statistics Definitions > What is a Rate Parameter? The term “rate parameter” can mean several different things, depending on the context. The most common use is to describe exponential distributions or event rates in Poisson processes. Use In Exponential Distributions Perhaps the most common use is as an alternative to the scale parameter in some … Read more