Statistics How To

Statistics Definitions > Homogeneity & Homogeneous Data What is Homogeneity? A data set is homogeneous if it is made up of things (i.e. people, cells or traits) that are similar to each other. For example a data set made up of 20-year-old college students enrolled in Physics 101 is a homogeneous sample. What is Homogeneous … Read more

Sampling > Voluntary Response Sample What is a Voluntary Response Sample? A voluntary response sample is a sample made up of volunteers. Compared to a random sample, these types of samples are always biased. For example, people who call in to a radio show poll may have strong opinions about a topic in either direction. … Read more

Statistics Definitions > What is a Two Way Table? A two way table is a way to display frequencies or relative frequencies for two categorical variables. One category is represented by rows and a second category is represented by columns. Example Sixty people (30 men and 30 women) were asked what type of movie they … Read more

Descriptive Statistics > Area Principle What is the Area Principle? The area principle states that the area of a graph should equal the magnitude of the data it is representing. For a simple example, let’s say you took three height measurements of 4 feet, 5 feet, and 6 feet. The top part of the image … Read more

Structural Equations Models > Latent Class Analysis / Modeling What is Latent Class Analysis? Latent Class Analysis (LCA) is a way to uncover hidden groupings in data. More specifically, it’s a way to to group subjects from multivariate data into “latent classes” — groups or subgroups with similar, unobservable, membership. Latent implies that the analysis … Read more

Statistics Definitions > Expected Monetary Value What is the Expected Monetary Value? The expected monetary value is how much money you can expect to make from a certain decision. For example, if you bet $100 that card chosen from a standard deck is a heart, you have a 1 in 4 chance of winning $100 … Read more

Statistics Definitions > Undercoverage definition What is Undercoverage? When some members of your population aren’t represented in a sample, it’s called undercoverage. In other words, some members of a population have zero chance of being included in the survey or experiment. It’s a type of selection bias that often occurs in convenience sampling, where you … Read more

Types of Variables > What are Identifier Variables? Identifier variables are categorical variables that have a single individual per category. For example: A Social Security Number. Interviewer ID number. Employee ID number. As identifier variables are singular, it’s impossible to perform any data analysis on them. Instead, they are used to identify results. For example, … Read more

Probability Distributions > Multimodal Distribution What is a Multimodal Distribution? A multimodal distribution is a probability distribution with more than one peak, or “mode.” A distribution with one peak is called unimodal A distribution with two peaks is called bimodal A distribution with two peaks or more is multimodal A bimodal distribution is also multimodal, … Read more

Types of Variables > Binary Variable What is a Binary Variable? A binary variable is a variable with only two values. For example: 1 / 0. Yes / No. Success / Failure. Male / Female. Black / White . Take the red pill, or the blue pill? Although binary variables are commonly used in statistics … Read more