First of all, what are parcels? Not the little packages your grandma left on the table in the hall when she came back from shopping. Well, not only that. In factor analysis, parcels are simply the sum of a small number of items. I prefer using parcels when possible because both basic psychometric theory and…
At first, I was thinking it wasn’t right to have a favorite paper, but then I realized that was idiotic. It’s not like these papers (or their presenters) are my children. My favorite paper was, Statistical modeling for large complex data: Five new directions from SAS/STAT software If you’re not a statistician, props to you…
The nice thing about going to SAS Global Forum is that it’s the gift that keeps on giving. Long after I have gone home, there are still points to ponder. Visual analytics is big and not just in the sense of there is a product out called that which I have never used but that…
If you did not go to SAS Global Forum this week, here are some things you missed: Me, rambling on about the 13 techniques all biostatisticians should know, including the answer to: If McNemar and Kappa are both statistics for handling correlated, categorical data, how can they give you completely different results? The answer is…
Esteemed statistics guru, Dr. Nathaniel Golden has some sobering news for Democrats. His latest models predict a Republican blow out. As can be seen by the map below, the Republican front-runner has tapped into the mood of resentment in the country’s non-elites. When the dust has settled, only the two highest earning states in the…
I can’t believe I haven’t written about this before – I’m going to tell you an easy (yes, easy) way to find and communicate to a non-technical audience standardized mortality rates and relative risk by strata. It all starts with PROC STDRATE . No, I take that back. It starts with this post I wrote…
SENSITIVITY AND SPECIFICITY – TWO ANSWERS TO “DO YOU HAVE A DISEASE?” Both sensitivity and specificity address the same question – how accurate is a test for disease – but from opposite perspectives. Sensitivity is defined as the proportion of those who have the disease that are correctly identified as positive. Specificity is the proportion…
Policy makers have very good reason for wanting to know how common a condition or disease is. It allows them to plan and budget for treatment facilities, supplies of medication, rehabilitation personnel. There are two broad answers to the question, “How common is condition X?” and, interestingly, both of these use the exact same SAS…
Who was it that said asking a statistician about sample size is like asking a jeweler about price. If you have to ask, you can’t afford it. We all know that the validity of a chi-square test is questionable if the expected sample size of the cells is less than five. Well, what do you…
Recall that in the last post we were using SAS functions to score a test that had been completed by middle school and upper elementary students. Since we wanted to make it as easy as possible for students to enter their answers, we accepted just about any format. Picking up where we left off ……