5 feet 8¼ inches (173.4 cm) which value he called the mediocrity. He found that
children of very tall mid-parents were generally taller than this mediocrity but not
as tall as their mid-parents, while shorter children were taller than their mid-
parents but shorter than the mediocrity. In other words, the children’s heights
regressed towards the mediocrity. It’s a bit like top class batter Alex Rodriguez’s
performances for the New York Yankees. His batting average in an exceptional
season is likely to be followed by an inferior average in the next, yet overall
would still be better than the average for all players in the league. We say his
batting average has regressed to the average (or mean).
Regression is a powerful technique and is widely applicable. Let’s suppose
that, for a survey, the operational research team of a popular retail chain chooses
five of its stores, from small outlets (with 1000 customers a month) through to
mega-stores (with 10,000 customers a month). The research team observes the
number of staff employed in each. They plan to use regression to estimate how
many staff they will need for their other stores.
marcin
(Marcin)
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