rules of thumb

How Big of a Sample Size do you need for Factor Analysis?

August 21st, 2020 by

Most of the time when we plan a sample size for a data set, it’s based on obtaining reasonable statistical power for a key analysis of that data set. These power calculations figure out how big a sample you need so that a certain width of a confidence interval or p-value will coincide with a scientifically meaningful effect size.

But that’s not the only issue in sample size, and not every statistical analysis uses p-values.

Chi-Square Test of Independence Rule of Thumb: n > 5

July 15th, 2020 by

Ever hear this rule of thumb: “The Chi-Square test is invalid if we have fewer than 5 observations in a cell”.

I frequently hear this mis-understood and incorrect “rule.”

We all want rules of thumb even though we know they can be wrong, misleading, or misinterpreted.

Rules of Thumb are like Urban Myths or like a bad game of ‘Telephone’.  The actual message gets totally distorted over time.

What is Kappa and How Does It Measure Inter-rater Reliability?

May 20th, 2020 by

The Kappa Statistic or Cohen’s* Kappa is a statistical measure of inter-rater reliability for categorical variables. In fact, it’s almost synonymous with inter-rater reliability.

Kappa is used when two raters both apply a criterion based on a tool to assess whether or not some condition occurs. Examples include:

Member Training: Statistical Rules of Thumb: Essential Practices or Urban Myths?

March 1st, 2017 by

There are many rules of thumb in statistical analysis that make decision making and understanding results much easier.

Have you ever stopped to wonder where these rules came from, let alone if there is any scientific basis for them? Is there logic behind these rules, or is it propagation of urban legends?

In this webinar, we’ll explore and question the origins, justifications, and some of the most common rules of thumb in statistical analysis, like: