Statistics How To

Statistics Definitions > Latent Semantic Analysis What is Latent Semantic Analysis? Latent Semantic Analysis (LSA) is a way to analyze how words and groups of words are used in texts. It is used to answer questions like: What is the underlying meaning of the text? What effect do words have on the meaning of passages? … Read more

Types of Variables > Nuisance Variable What is a Nuisance Variable? Starting off, a nuisance variable is a type of extraneous variable that causes an increase in variability within groups in an experiment. Following this, these variables tend not to differ between levels of an independent variable (like confounding variable), but they increase variability of … Read more

Probability > Decision Tree What is a Decision Tree? A decision tree is a very specific type of probability tree that enables you to make a decision about some kind of process. For example, you might want to choose between manufacturing item A or item B, or investing in choice 1, choice 2, or choice … Read more

Statistics Definitions > STEN Score You may find it helpful to read this article first: What is a Bell Curve? What is a STEN score? STEN scores (or “Standard Tens”) divide a scale into ten units. In simple terms, you can think of them as “scores out of ten”: A STEN of 1 or 2 … Read more

Statistics Definitions > Design Effect What is a Design Effect? A design effect(DEFF) is an adjustment made to find a survey sample size, due to a sampling method (e.g. cluster sampling, respondent driven sampling, or stratified sampling) resulting in larger sample sizes (or wider confidence intervals) than you would expect with simple random sampling(SRS). The … Read more

Time series > Autoregressive Model What is an Autoregressive Model? An autoregressive (AR) model predicts future behavior based on past behavior. It’s used for forecasting when there is some correlation between values in a time series and the values that precede and succeed them. You only use past data to model the behavior, hence the … Read more

Statistics Definitions > Within Mean Square What is Within Mean Square? Within Mean Square (WMS) is an estimate of the population variance. It is based on the average of all variances within the samples. Within Mean is a weighted measure of how much a (squared) individual score varies from the sample mean score (Norman & … Read more

Descriptive Statistics > Shapes of Distributions What Defines Shapes of Distributions? When a data set is graphed, each point is arranged to produce one of dozens of different shapes. The distribution shape can give you a visual which helps to show how the data is: Spread out (e.g. dispersion, variability, scatter), Where the mean lies, … Read more

Hypothesis Testing > Unequal Sample Sizes Problems with Unequal Sample Sizes Unequally sized groups are common in research and may be the result of simple randomization, planned differences in group size or study dropouts. Unequal sample sizes can lead to: Unequal variances between samples, which affects the assumption of equal variances in tests like ANOVA. … Read more

Hypothesis Testing > Testing a Single Mean When you test a single mean, you’re comparing the mean value to some other hypothesized value. Which test you run depends on if you know the population standard deviation(σ) or not. Known population standard deviation If you know the value for σ, then the population mean has a … Read more