Star Atlases & Books

Graph error bars

You often print graphs in which data points have error bars that are too short. About a third of the error bars don’t overlap the line of best fit. So which is wrong? Neither! When it comes to describing statistical uncertainty, such as drawing an error bar, the usual measure is plus or minus...

How many digits are satisfactory in the measurement of pi?

In the 3rd century BC, Archimedes proved that the ratio of a circle’s circumference to its diameter is less than 3 1/7 but larger than 3 10/71. That’s about 3.141. Later mathematicians have computed what we now call p (pi) to greater and greater accuracy — but how many digits are “enough”? The answer...