At the JMP seminar on Monday, when Dick De Veaux said that 65-70% of time in all research projects is spent on data cleaning, everyone in the audience groaned in agreement. One of the biggest problems I run into is recoding those simple textboxes. For example, we often want to look at data for one…
The model is non-significant, therefore my theory is supported. Huh? Just when you thought it was safe to get back into statistics… It took you two years of graduate school but now you have it down. P-value low = good, relationship detected, publication, tenure, Abercrombie & Fitch models at your feet. P-value = high, no…
Lately I have been on a roll looking at relatively less common statistical techniques, proportional hazards, survival analysis, etc. In keeping with that, I have been taking a look at propensity score matching, fondly known as PSM by, – well, by no one actually. The problem to be solved …. Think about some of these…
Event history models of all types have a few characteristics that make them unique. First of all, forget that whole symmetry thing around zero. Here our dependent variable of interest is time to event. We are interested in how long a person lives, remains sober, stays with a given company, or, in a study of…
What is an event history model? Think of it like this – you are interested in whether something happens, what predicts whether it happens and how long until it happens. Let’s take a common one, like, say, death. An event history model could predict the duration from diagnosis of tuberculosis to death. In this model…
I will be finishing reading thousands of pages of grants and spend a few days on grant reviews. A grant I have been working on is almost done. The semester is almost over. I have two articles I submitted to journals under review. So… the question is, what’s next? I thought about trying to make…
Since I have written about odds ratios and logs lately, I was going to write about the natural log of the odds ratio, however, random events have caused me to do otherwise. I read an interesting blog by Adam Jackson lately, in which he is concerned that robots will take over the world. At the…
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…
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…
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…