Why randomness doesn’t always look random

I got the lightning puzzle that I posed yesterday from the latest book by Steven Pinker The Better Angels of Our Nature: Why Violence Has Declined that I reviewed in December. He uses it to illustrate that our intuitive notions of randomness and probability can easily lead us astray.

Here is the problem again.

Suppose you live in a place that has a constant chance of being struck by lightning at any time throughout the year. Suppose that the strikes are random: every day the chance of a strike is the same, and the rate works out to one strike a month. Your house is hit by lightning today, Monday. What is the most likely day for the next bolt to strike your house?

Here is his answer followed by [Read more…]

When is lightning most likely to strike again?

Since I have been taking about probabilities recently, here is a little puzzle for people to ponder overnight.

Suppose you live in a place that has a constant chance of being struck by lightning at any time through the year. Suppose that the strikes are random: every day the chance of a strike is the same, and the rate works out to one strike a month. Your house is hit by lightning today, Monday. What is the most likely day for the next bolt to strike your house?

Feel free to post your answers in the comments. I will give the answer tomorrow along with a discussion.

Blogs with homework. Now there’s a novel concept!

Update: The solution and discussion are posted here.

Probabilities and false positives

In response to my post on random drug testing in Florida, commenter Scott mentioned the danger of false positives and said that a second test in his case cleared him of having taken drugs. My advice to anyone is that whenever you take a high-stakes test for anything that has a small incidence in the general population (drugs, diseases, whatever) and it comes out positive, always consider asking for a second test.

Here’s why. [Read more…]

An old Earth, population bottlenecks, and Adam and Eve

It is always interesting to see religious people trying to find ways to reconcile modern science with their religious texts. For people who have a literal interpretation of the Bible, the task is much harder, with the Genesis story being a nightmare. This is not because the Genesis story is particularly crazier than the other miraculous stories in the Bible but because it is the most familiar and you cannot easily finesse it away. Everyone knows the general outlines of it, even if they are [Read more…]

Do scientists get less religious as they get older?

In a comment to the earlier post on Einstein’s view of god, reader M. Nieuweboer pointed out that as Einstein got older, he seemed to dissociate himself more and more from religion and the idea of a god, and became more explicit in rejecting attempts to make him seem religious.

This comment piqued my interest and I began to wonder if there was a correlation between the age of scientists and their levels of disbelief. As a personal aside, I myself [Read more…]

What your major says about your family members

I came across a study that reports:

We surveyed an entire class of high-functioning young adults at an elite university for prospective major, familial incidence of neuropsychiatric disorders, and demographic and attitudinal questions. Students aspiring to technical majors (science/mathematics/engineering) were more likely than other students to report a sibling with an autism spectrum disorder (p=0.037). Conversely, students interested in the humanities were more likely to report a family member with major depressive disorder (p=8.8×10−4), bipolar disorder (p=0.027), or substance abuse problems (p=1.9×10−6).

Since my older daughter majored in engineering and the younger in humanities, that must mean that our family has a good chance of developing a fairly good set of neuropsychiatric disorders, no?

Has global warming tapered off?

Observational or experimental data, if plotted on a graph, consist of a set of discrete points. There are potentially an infinite number of lines that can be drawn through those points. In some cases, the data itself suggests an overall rising or lowering trend but whether the relationship is a simple linear one or more complicated is not often easily discernible with the naked eye. We have to impose a curve based on prior expectations of [Read more…]