That’s Smooth

I had someone ask me the other day how to take a scatterplot and draw something other than a straight line through the graph using Excel.  Yes, it can be done in Excel and it’s really quite simple, but there are some limitations when using the stock Excel dialog screens. So it is probably in… Read More »

The Uncertainty of Predictions

There are many kinds of intervals in statistics.  To name a few of the common intervals: confidence intervals, prediction intervals, credible intervals, and tolerance intervals. Each are useful and serve their own purpose. I’ve been recently working on a couple of projects that involve making predictions from a regression model and I’ve been doing some… Read More »

Waiting in One Line or Multiple Lines

Whenever I go to the grocery store it always seems to be a lesson in statistics. I go get the things I need to buy and then  I try to select the checkout register that will decrease the amount of time I have to wait. Inevitably, I select the one line where there is some… Read More »

A Monty Simulation

I was listening to Science Friday from Sep 6th. and one of the discussions by Ira Flatow was on the well known Monty Hall Problem.  This problem has been hashed out many times and in fact I was first introduced to the probability aspects of the problem while taking my introductory to statistics class when… Read More »

The Eve of the NYC Democratic Mayoral Primary Election

It is the eve of the New York City Democratic mayoral primary election.  This is a simple follow-up on my post from last Friday as I was curious how the final pre-Election Day polling was going to fall.  It’s fairly clear who is going to get the most votes.  Though we have a very good… Read More »

The Beta Prior, Likelihood, and Posterior

The Beta distribution (and more generally the Dirichlet) are probably my favorite distributions.  However, sometimes only limited information is available when trying set up the distribution.  For example maybe you only know the lowest likely value, the highest likely value and the median, as a measure of center.  That information is sufficient to construct a… Read More »

Passing-Bablok Regression: R code for SAS users

While at the Joint Statistical Meeting a few weeks ago I was talking to a friend about various aspects to clinical trials. He indicated that no current R package was able to perfectly reproduce Passing-Bablok (PB) regression so that it exactly matched SAS. He ultimately wrote a couple of functions and kindly shared them with… Read More »

When Discussing Confidence Level With Others…

This post spawned from a discussion I had the other day. Confidence intervals are notoriously a difficult topic for those unfamiliar with statistics. I can’t really think of another statistical topic that is so widely published in newspaper articles, television, and elsewhere that so few people really understand. It’s been this way since the moment… Read More »