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Logarithms

Logistic regression is based on logarithms. Ordinary Least Squares regression and analysis of variance uses the actual values as the dependent and independent variables in an equation. Logistic regression does not. What is a log, anyway? Let’s start with the very basics. First we learned to add: 5+5+5+5 = 20 After about eight years of…

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Baby Steps to Logistic regression

Going from the phi coefficient to odds-ratios. Remember the numerator for the phi coefficient was well, the odds ratio is the same two numbers DIVIDED rather than subtracted. You might think it is four numbers, but really it is not. The first number is the product of the diagonal cells (see below). The second number…

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Phi coefficients, odds ratios and the F-word

Yes, I am the F-word – a feminist. I was at a faculty meeting this weekend and one of the presenters began by saying, pointing to a colleague in the audience, “I am sure Dr. Y knows more about this than me.” Several times in her presentation on analysis of assessment data she would pause…