Month: December 2018

The graph below presents average scores on a test at baseline (time 1), after training (time 2) and at follow up. Did the training help? Looks like it. But did it really? Now how about this barchart: This program doesn’t look as impressive does it? In fact, it is exactly the same as the first ...

I often read and hear that people are living longer these days, that the average life expectancy has increased dramatically over the past 100 years or so. But this does not mean that in 1900 people were tending to drop dead by age 50. Life expectancy is typically expressed in terms of life expectancy at ...

This past Spring, a report released by the Stinson Center, a non-partisan policy research organization showed that the United States has spent about $2.8 trillion counter-terrorism related activities since the Sept. 11, 2001, terrorist attacks. That is a stunningly high, difficult to conceptualize figure. In 2017 total spending exceeded $174 billion dollars. Another stunningly high, ...

When meteorologists say there is a 30% chance that it will rain today, what exactly do they mean? I will pause a second to let you think of your answer. – 30% of the day?– 30% of the region?– 30% of meteorologists? None of these. In fact, it means that for a given area, it ...

Say we are reading about a recently completed trial investigating a new flu vaccine. At the beginning of the flu season, they randomly assigned 200,000 participants to be injected either with the experimental vaccine or a placebo (a saline solution only), winding up with 100,000 in each group. By the end of the flu season, of ...

With very few exceptions (the national census is one notable example), studies use samples drawn from a population. Political polls attempt to learn about attitudes towards various issues not by asking every adult in the country but by taking a sample. A drug company conducting a randomized clinical trials on a new analgesic will select ...

A female patient, 55 years of age, has taken a mammography and the test comes back positive for breast cancer. You understand that the mammography catches about 90% of breast cancers. Given this test result, what is the probability that the patient in fact has cancer? A similar question was posed to 160 gynecologists and ...