Statistics How To

Estimators > German Tank Problem German Tank Problem The German Tank Problem is a way to estimate the total population size from a small sample. It’s commonly used in AP statistics to teach about estimators. The problem was originally developed by the Allies during World War II, when it was used to estimate the total … Read more

Descriptive Statistics > Lag Plot What is a Lag Plot? A lag plot is a special type of scatter plot with the two variables (X,Y) “lagged.” A “lag” is a fixed amount of passing time; One set of observations in a time series is plotted (lagged) against a second, later set of data. The kth … Read more

Bias > Reporting Bias What is Reporting Bias? Reporting bias (also called selective reporting) affects which studies “come to light” and which do not. Studies might be selected (or not selected) for a myriad of reasons including personal agendas, lack of knowledge, or sloppy analysis methods. This type of bias is a substantial problem in … Read more

Statistics Definitions > Orthogonality What is Orthogonality in Statistics? Simply put, orthogonality means “uncorrelated.” An orthogonal model means that all independent variables in that model are uncorrelated. If one or more independent variables are correlated, then that model is non-orthogonal. The term “orthogonal” usually only applies to classic ANOVA. An orthogonal ANOVA has all categorical … Read more

Probability and Statistics > Regression analysis > General Linear Model (GLM) What is a General Linear Model? The General Linear Model (GLM) is a useful framework for comparing how several variables affect different continuous variables. In its simplest form, GLM is described as: Data = Model + Error (Rutherford, 2001, p.3) GLM is the foundation … Read more

Regression Analysis > Beta Weight What is a Beta Weight? A beta weight is a standardized regression coefficient (the slope of a line in a regression equation). They are used when both the criterion and predictor variables are standardized (i.e. converted to z-scores). A beta weight will equal the correlation coefficient when there is a … Read more

Bias > Publication Bias What is Publication Bias? Publication bias is when studies with positive findings are more likely to be published — and they tend to be published faster — than studies with negative findings. This means that any meta analysis or literature reviews based only on published data will be biased, so researchers … Read more

Descriptive Statistics > Funnel Plot What is a Funnel Plot? A funnel plot is a scatter plot of individual studies, their precision and results. Funnel plots have the following characteristics: Each dot represents a single study. The y-axis is usually the standard error of the effect estimate. Larger studies with higher power are placed towards … Read more

Bias in Statistics > Location Bias What is Location Bias? Loosely speaking, location bias means that there’s a tendency towards a particular location or certain area. “Location” could mean an online or a physical location. For example: Online databases are more likely to index articles from well-known journals, Google provides search results based on your … Read more

Statistics Definitions > Contents: Percent Error Percent Difference What is Percent Error? Watch the video for an overview of percent error and percent difference: Can’t see the video? Click here to watch it on YouTube. Percent errors tells you how big your errors are when you measure something in an experiment. Smaller values mean that … Read more