Statistics How To

Statistics Definitions > Effect Size / Measurement of Association Before reading this article, you may want to review: What is a p value?. The terms “Measure of Association” and “Effect Size” both mean the same thing: quantifying the relationship between two groups. It’s more common to talk about Effect Size in the medical field, when … Read more

Statistics Definitions > Construct Validity What is a Construct? When you’re talking about a construct in relation to testing and construct validity, it has nothing to do with the way a test is designed or constructed. A construct is something that happens in the brain, like a skill, level of emotion, ability or proficiency. For … Read more

Statistics Definitions > Parametric Statistics What are “Parametric Statistics”? Parametric can refer to (click to skip to the section): Parametric Statistical Tests Parametric Data Parametric Equations Parametric Statistical Tests A parameter in statistics refers to an aspect of a population, as opposed to a statistic, which refers to an aspect about a sample. For example, … Read more

Descriptive Statistics: Charts, Graphs and Plots > Types of Graphs Common Types of Graphs Contents (click to skip to the section): Bar Graph Segmented Bar Graph Column Graph Box and Whiskers Graph (also called a Box Plot) Frequency Graph (Frequency Table) Cumulative Frequency Table Frequency Polygon Histogram Line Graph Timeplot Relative Frequency Histogram Pie Chart … Read more

Statistics Definitions > Internal Validity What is Internal Validity? Note: If you aren’t familiar with confounding, read this article first: Confounding Variables Internal validity is a way to measure if research is sound (i.e. was the research done right?). It is related to how many confounding variables you have in your experiment. If you run … Read more

Statistics Definitions > Causation What is Causation? According to Merriam-Webster, causation is “the act or process of causing something to happen or exist.” In other words, causation means one event is 100 percent certain to cause something else. If you paint, you’ll make a painting. If you stand in the rain, you’ll get wet. On … Read more

Types of Variable > Manipulated Variable What is a Manipulated Variable? A manipulated variable is the independent variable in an experiment. It’s called “manipulated” because it’s the one you can change. In other words, you can decide ahead of time to increase it or decrease it. In an experiment you should only have one manipulated … Read more

Types of Variable > Intervening Variable What is an Intervening Variable? An intervening variable is a hypothetical variable used to explain causal links between other variables. Intervening variables cannot be observed in an experiment (that’s why they are hypothetical). For example, there is an association between being poor and having a shorter life span. Just … Read more

Statistics Definitions > Fisher’s Exact Test of Independence What are nominal variables? What is a contingency table? In order to understand Fisher’s, you may want to read these articles first: What is Fisher’s Exact Test of Independence? Fisher’s Exact Test of Independence is a statistical test used when you have two nominal variables and want … Read more

Statistics Definitions > Median Absolute Deviation What is the Median Absolute Deviation The median absolute deviation(MAD) is a robust measure of how spread out a set of data is. The variance and standard deviation are also measures of spread, but they are more affected by extremely high or extremely low values and non normality. If … Read more