Statistics How To

Statistics Definitions > Rank Histogram What is a Rank Histogram? Rank histograms (sometimes called verification rank histograms or Talagrand diagrams) are a way to show how reliable an ensemble forecast is compared to a set of newly observed data. In other words, they show the bias for the model. If an ensemble forecast is accurate, … Read more

Measurement Error > Absolute Error What is Absolute Error? Absolute Error is the amount of error in your measurements. It is the difference between the measured value and “true” value. For example, if a scale states 90 pounds but you know your true weight is 89 pounds, then the scale has an absolute error of … Read more

Estimators > Shrinkage Estimator What is Shrinkage? Shrinkage is where extreme values in a sample are “shrunk” towards a central value, like the sample mean. Shrinking data can result in: Better, more stable, estimates for true population parameters, Reduced sampling and non-sampling errors, Smoothed spatial fluctuations. However, the method has many disadvantages, including: Serious errors … Read more

Estimators > James-Stein Estimator What is the James-Stein Estimator? It’s common in statistics to take averages to make predictions. For example, the sample mean (the average score from all samples) is used as an estimator for the population mean. James-Stein estimators improve upon these averages by shrinking them towards a more central average. The technique … Read more

Statistics Definitions > Deterministic What is Deterministic? Deterministic (from determinism, which means lack of free will) is the opposite of a random event. It tells us that some future event can be calculated exactly, without the involvement of randomness. For example, the conversion between Celsius and Kelvin is deterministic, because the formula is not random…it … Read more

Descriptive Statistics > Forest Plot / Blobbogram What is a Forest Plot / Blobbogram? A blobbogram (sometimes called a forest plot) is a graph that compares several clinical or scientific studies studying the same thing. Originally developed for meta-analysis of randomized controlled trials, the forest plot is now also used for a variety of observational … Read more

Statistics Definitions > Heterogeneity What is Heterogeneity? Heterogeneity in statistics means that your populations, samples or results are different. It is the opposite of homogeneity, which means that the population/data/results are the same. A heterogeneous population or sample is one where every member has a different value for the characteristic you’re interested in. For example, … Read more

Statistics Definitions > Statistical Treatment What is Statistical Treatment? Statistical treatment can mean a few different things: In Data Analysis: Applying any statistical method — like regression or calculating a mean — to data. In Factor Analysis: Any combination of factor levels is called a treatment. In a Thesis or Experiment: A summary of the … Read more

Hypothesis Testing > Welch’s ANOVA What is Welch’s ANOVA? Welch’s ANOVA compares two means to see if they are equal. It is an alternative to the Classic ANOVA and can be used even if your data violates the assumption of homogeneity of variances. You should run Welch’s test in all cases where you have normally … Read more

Types of Graph > Funnel Chart Funnel Chart Funnel charts can be used to illustrate stages in a process — usually sales processes. However, they could be used to show anything that’s decreasing in size. For example, you can use this type of chart to show: An order fulfillment process. A sales process from start … Read more