Hey, if you are a furloughed federal employee looking for something free to do on Thursday because you still haven’t received your back pay that Congress promised you, you can drop on into Salem, Oregon to the Oregon SAS Conference. I will be speaking on Categorical Data Analysis, Telling Stories with Your Data and How…
While I love teaching and am looking forward to be working in a completely new environment – teaching an online course to masters students – I was initially concerned that teaching a course on biostatistics in public health might draw too much time away to my work for The Julia Group. I really should have…
Box and whisker plots can give you an understanding of your data at a glance – IF you know what you’re looking at. The BOX extends from the 25th percentile to the 75th percentile. That line in the middle is the median, also known as the 50th percentile. The diamond inside the box is the…
What is item difficulty analysis and how is it helpful? Item difficulty analysis is simply examining what percentage of students answered each item correctly. Item difficulty analysis is one basic way to establish test validity. One would expect that items at the second-grade level would have the lowest level of difficulty, being answered by the…
Ever since my daughters referred to the day in April when we all take our kids to the office as “Bore your daughters at work day”, it has been clear to me that others do not find me as interesting as I find myself. Based on this profound knowledge, when I was asked to talk…
This is the third and last part of my attempt to explain logistic regression in pictures. You can see a picture of odds ratios here, and a picture of two charts of predicted probabilities, to compare models, here. If people only know one chart associated with logistic regression, it is usually the ROC chart, though…
I tweeted that I believed one could explain logistic regression results in three or four charts, and Alberta Soranzo tweeted back, “Try me.” Challenge accepted. These data are taken from the Kaiser-Permanente study of the Oldest Old, a sample of 5,986 people who were aged 65-95 when recruited into the study. Participants were followed for…
One nice thing that SAS Enterprise Guide does is produce a series of graphs when you do a logistic regression. Too many people just skim over the table of Type III effects, say what is significant and isn’t and go on their merry way, which is too bad, because sometimes your graphs are very easy…
A two-by-two table is a very common design. The column variable is some type of treatment or intervention. For example, older (over 65 years of age) people who either lived in a nursing home or who did not. Your row variable is some categorical outcome. For example, they either lived or died. You create a…
I’ve been working with SAS Enterprise Guide 6.1 with SAS On-Demand on Virtual Box and I can’t find much to complain about. It is slow, but since I’m usually doing 14 things at once, while I’m writing for a task to complete I can read an email, download a file or answer a phone call….