Illinois State University Department of Mathematics
|Here are links to the whole story:
Tuesday 2/18/14: An informative NPR
story about our country's less-than-successful
transition to CFL and LED light bulbs.
Wednesday 2/19/14: Roger Day offers up story correction to Robert Siegal
Thursday 2/20/14: NPR corrects the light-bulb
to or read
the NPR correction.
I enjoyed and
learned from yesterday's (2/18/14) story on the slow and
less-than-successful transition to non-incondecsent light
At one point in the story, Robert Siegal was
introducing an expert who described how life-span estimates
are calculated for bulbs. Robert mentioned that a MEAN is
computed and then introduced the expert. The expert
described the process of obtaining a large number of bulbs,
switching them all on, and then measuring time until exactly
half the bulbs remained lit (or half had burned out).
This time measure, of course, is the MEDIAN, the
physical middle of a data set! A MEAN couldn't have been
computed until all bulbs had burned out, because the MEAN
requires all values to be known, as we sum the values (burn
times, here), and divide by the number of values (here, the
total number of bulbs tested).
Thanks for setting the record straight!
Roger Day, Mathematics Department, Illinois
Return to story chronology.