Beta Distribution and the NJ U.S. Senate Election

The beta distribution is highly flexible distribution and applies to many situations and environments. The beta distribution applies well when there are percentages. The upcoming New Jersey U.S. Senate election on Wednesday fits that criterion quite well. So here I applied the beta distribution to some pre-election polls where the numbers were obtained through the… Read More »

Random Sequence of Heads and Tails: For R Users

Rick Wicklin on the SAS blog made a post today on how to tell if a sequence of coin flips were random.  I figured it was only fair to port the SAS IML code over to R.  Just like Rick Wicklin did in his example this is the Wald-Wolfowitz test for randomness.  I tried to… Read More »

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 »