This is one example of selection bias. Selection bias is when the probability of something being chosen in a random sample is related to whatever you’re measuring. Let’s say you’re measuring the average wealth in the USA. But instead of using the census, you just ask a bunch of people at a yacht club. Your sample will obviously be biased, because someone at the yacht club is more likely to be rich. Or say you conduct a survey to see how phone numbers an average person has. You do this by selecting seven random digits and calling them. This is also biased. Those with more phone numbers are more likely to be picked for the survey.
More germane to the article I linked to, when you run or bike outdoors, you really are hitting the hard parts more than the easy. Let’s say you bike a circular course in and around the city that eventually takes you home. Obviously your net elevation change was zero. You went just as far down as up (after all, you ended up at the same point). So how can I say more of it is uphill? Because when the course is downhill, you go fast. When it’s uphill, you go slow. So at any given time, you’re more likely to be going uphill than downhill. You spend more of your time struggling up than coasting down.
There’s probably a life lesson there somewhere. Take your pick!
1) Everyone must persevere against what life offers, the struggle is what makes the race worth running.
2) Everyone’s life stinks just as bad as yours.
3) No one said that life isn’t fair.
4) Exercise is for chumps.
Update: Or another example, a CNN poll showing that 79% of those watching Bush’s speech approved of it. Gee, you think there might be a connection there of some kind?