Statistics How To

Probability > Joint Probability / Joint Distribution What is Joint Probability? Can’t watch the video? Click here. Joint probability is the probability of two events happening together. The two events are usually designated event A and event B. In probability terminology, it can be written as: p(A and B)  or  p(A ∩ B) Joint probability … Read more

Probability distributions > Unusual Probability Distributions These unusual probability distributions (or unusual names for distributions) never made it to the mainstream. You won’t find these in your regular textbooks, but I did come across this interesting list put together by Prof. Shakti [1]. List of Unusual Probability Distributions The array distribution refers to the conditional … Read more

Probability Distributions > Pearson Distribution What is the Pearson Distribution? The Pearson distribution (sometimes called the Pearson system of distributions) is a family of unimodal continuous probability distribution functions that satisfy the following differential equation: Pearson described twelve families of distributions as solutions to the equation. His original paper, (1895, p. 360) identified four (numbered … Read more

SPSS > Missing Values SPSS Example You’ll often have missing values in your data, especially when conducting research. For example, a respondent might not answer every question in a survey, or you might make errors when entering your data. In this example SPSS dataset, I have three different types of data representing the three variable … Read more

Confidence Intervals > Wilson CI (also called “plus-4” confidence intervals or Wilson Score Intervals) are Wald intervals computed from data formed by adding 2 successes and 2 failures. The Wilson confidence intervals [1] have better coverage rates for small samples. For example, you might be expecting a 95% confidence interval but only get 91%; the … Read more

Statistics Definitions > The sample proportion (p̂) describes the proportion of individuals in a sample with a certain characteristic or trait. To find the sample proportion, divide the number of people (or items) who have the characteristic of interest by the total number of people (or items) in the sample. For example, let’s say you … Read more

Effect Size > Omega Squared Contents: What is Omega Squared? Formula Interpreting Results Omega Squared in SPSS What is Omega Squared? Omega squared (ω2) is a measure of effect size, or the degree of association for a population. It is an estimate of how much variance in the response variables are accounted for by the … Read more

Statistics Definitions > Chance vs Probability vs Odds Probability is the study of the chance something will happen. The two terms—chance and probability—are often used as synonyms. If you’re talking about the chance something will happen, then that is an informal way of saying probability. For example, you might say you have a 10% chance … Read more

Probability in Real Life Expected value tells you the return you can expect for some kind of action. For example, if you spend $10 on Powerball tickets every week, how much money can you expect to win or lose? We can answer that question with probability, which allows us to create a formula for Powerball … Read more

Probability in Real Life > The odds of winning a jackpot in a national lottery are so slim (one in several hundred millions), that it’s often a better bet to play the state lotteries, like Fantasy Five, instead of the national ones. Why are the Fantasy Five odds better? Let’s take a look at the … Read more