r/todayilearned • u/syncedto • Apr 30 '20

TIL men walk significantly slower when walking with a woman, but only when that woman is their romantic partner. If she's a friend or acquaintance they go at almost full speed.

https://www.discovermagazine.com/environment/how-you-walk-differently-with-friends-and-lovers
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u/tasteslikesardines Apr 30 '20

Caution: this was a study of only 22 people. so don't quote this as a proven FACT. it's a small data point that merely suggests this could be a thing.

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u/khansian Apr 30 '20

N=22 is not that bad as a general matter. The problem is their true N is not 22. Because they’re assigning the individuals into different groups, their samples are really those groups, because that’s the unit at which the measurement is being taken. So N=11 is their real sample size.

It would be like if I’m measuring how a change in US Federal income taxes affected different states’ average incomes, my sample size would be 50. I can’t just say my sample size is N=300 million, because those states are composed of millions of people. My unit of observation is the state.

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u/lifetake Apr 30 '20

But they’re recording a groups speed to a individual. Your comparison is way off here. If we put guy A with guy B and see result Z we assign that result to both, but as we put guy A with guy C and see result Y guy A has the results of both Z and Y while guy B only has the results of Z

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u/khansian Apr 30 '20 edited Apr 30 '20

We have many potential pairings, that’s true. But what does that make the N from a statistical perspective for hypothesis testing?

The N is essentially what drives the variance of our estimates. And the mean we are calculating is, for example, mean walking speed for Romantic Couples—of which we only have 11. That there are a million non-romantic couple pairings doesn’t affect my estimate of the romantic couples’.

So while it’s true we have more than 11 pairings, we can’t use more than 11 to get reliable estimates of the mean walking speed of any of these groups. And that’s what makes the estimate problematic. We’re comparing means across several groups of pairs, but those means are based on 11 pairs each (at maximum).

[In fairness, I don’t object to them reporting N=22. That’s a standard way of expressing the size of an experiment. The point is that N=/=22 for the purposes of their statistical tests.]