Statistics How To

Sampling > Sampling Distribution of the Sample Proportion The Sampling Distribution of the Population Proportion gives you information about the population proportion, p. For example, you might want to know the proportion of the population (p) who use Facebook. You can’t survey everyone on the planet, so you use a sample and get the sample … Read more

Sampling > Finite Population Correction Factor What is the Finite Population Correction Factor? The Finite Population Correction Factor (FPC) is used when you sample without replacement from more than 5% of a finite population. It’s needed because under these circumstances, the Central Limit Theorem doesn’t hold and the standard error of the estimate (e.g. the … Read more

Normality > Lilliefors Test What is Lilliefors Test? The Lilliefors test is a test for normality. It is an improvement on the Kolomogorov-Smirnov (K-S) test — correcting the K-S for small values at the tails of probability distributions — and is therefore sometimes called the K-S D test. Many statistical packages (like SPSS) combine the … Read more

Statistics Definitions > Assumption of Normality / Normality Test What is Assumption of Normality? Assumption of normality means that you should make sure your data roughly fits a bell curve shape before running certain statistical tests or regression. The tests that require normally distributed data include: Independent Samples t-test. Hierarchical Linear Modeling. ANCOVA. Goodness of … Read more

Statistics Definitions > Implicit Factors What are Implicit Factors? Implicit factors imply some connection between items in a sample. If your sample has a lack of independence, that’s an indication that there may be one or more implicit factors in your sample. The word “factor” is extremely broad, and it means that practically anything can … Read more

Types of Probability Distribution > What is the Wishart Distribution? The Wishart distribution is one of the more complicated distributions in statistics, partly because there are many ways to define it. First of all, the simplest definition: it is the multivariate counterpart of a chi-squared distribution when the degrees of freedom are not integers. For … Read more

Probability > Prior Probability: Uniformative, Conjugate What is Prior Probability? Prior probability is a probability distribution that expresses established beliefs about an event before (i.e. prior to) new evidence is taken into account. When the new evidence is used to create a new distribution, that new distribution is called posterior probability. In some ways, it’s … Read more

Regression Analysis > Spurious Correlation What is a Spurious Correlation? A spurious correlation wrongly implies a cause and effect between two variables. For example, the number of astronauts dying in spacecraft is directly correlated to seatbelt use in cars: This graph — showing that an increase in car seat belt results in a lower number … Read more

Statistics Definitions > Classical Probability Contents: What is Classical Probability? Classical Probability Examples in Real Life What is Classical Probability? Classical probability is a simple form of probability that has equal odds of something happening. For example: Rolling a fair die. It’s equally likely you would get a 1, 2, 3, 4, 5, or 6. … Read more

Hypothesis Testing > Sign Test What is the Sign Test? The sign test compares the sizes of two groups. It is a non-parametric or “distribution free” test, which means the test doesn’t assume the data comes from a particular distribution, like the normal distribution. The sign test is an alternative to a one sample t … Read more