Statistics How To

Design of Experiments > Counterbalancing What is Counterbalancing? Counterbalancing removes confounding variables from an experiment by giving slightly different treatments to different participant groups. For example, you might want to test whether people react positively or negatively to a series of images. They use a left-hand clicker for positive, and a right-hand clicker for negative. … Read more

Statistics Definitions > Fisher Z-Transformation What is Fisher Z-Transformation? The Fisher Z-Transformation is a way to transform the sampling distribution of Pearson’s r (i.e. the correlation coefficient) so that it becomes normally distributed. The “z” in Fisher Z stands for a z-score. The formula to transform r to a z-score is: z’ = .5[ln(1+r) – … Read more

Inferential Statistics > Comparison of Means Comparison of Means Techniques There are many cases in statistics where you’ll want to compare means for two populations or samples. Which technique you use depends on what type of data you have and how that data is grouped together. The four major ways of comparing means from data … Read more

Sampling > Multistage Sampling What is Multistage Sampling? Multistage sampling divides large populations into stages to make the sampling process more practical. A combination of stratified sampling or cluster sampling and simple random sampling is usually used. Let’s say you wanted to find out which subjects U.S. school children preferred. A population list—a list of … Read more

Random Variables > Independent Random Variables You may want to read this article first: What is a Random Variable? What are Independent Random Variables? An independent random variable is a random variable that doesn’t have an effect on the other random variables in your experiment. In other words, it doesn’t affect the probability of another … Read more

Statistics Definitions > What is Statistical Analysis? Statistical analysis is the science of collecting data and uncovering patterns and trends. It’s really just another way of saying “statistics.” After collecting data you can analyze it to: Summarize the data. For example, make a pie chart. Find key measures of location. For example, the mean tells … Read more

Types of Variable > Dependent Variable Definition Contents (click to skip to the section): Dependent Variable General Definition. Dependent Variable Examples. Test Your Understanding. Dependent Variable Definition (Statistical Modeling). Dependent Variables in Psychology. Dependent Variables in Cross Tabs. Other Names for the Dependent Variable. Outcome Variable. Dependent Variable Definition. The dependent variable(DV) is just like … Read more

Types of Variable > Independent Variable Contents: Independent Variable Predictor Variable 1. Independent Variable Definition. Independent variables are variables that stand on their own and aren’t affected by anything that you, as a researcher, do. You have complete control over which independent variables you choose. During an experiment, you usually choose independent variables that you … Read more

Statistics Definitions A frequency polygon is very similar to a histogram. In fact, they are almost identical except that frequency polygons can be used to compare sets of data or to display a cumulative frequency distribution. In addition, histograms tend to be rectangles while a frequency polygon resembles a line graph. How to Make a … Read more

Statistics Definitions > Contour Plots What are Contour Plots? Contour plots (sometimes called Level Plots) are a way to show a three-dimensional surface on a two-dimensional plane. It graphs two predictor variables X Y on the y-axis and a response variable Z as contours. These contours are sometimes called z-slices or iso-response values. This type … Read more