Tag Archives: inference

Is “nearly significant” ridiculous?

Graphic: Parasitoid emergence from aphids on peppers, as a function of soil fertilization. Analysis courtesy of Chandra Moffat (but data revisualized for clarity).

“Every time you say ‘trending towards significance’, a statistician somewhere trips and falls down.” This little joke came to me via Twitter last month. I won’t say who tweeted it, but they aren’t alone: similar swipes are very common. I’ve seen them from reviewers of papers, audiences of conference talks, faculty colleagues in lab meetings, and many others. The butt of the joke is usually someone who executes a statistical test, finds a P value slightly greater than 0.05, and has the temerity to say something about the trend anyway. Sometimes the related sin is declaring a P value much smaller than 0.05 “highly significant”. Either way, it’s a sin of committing statistics with nuance.

Why do people think the joke is funny? Continue reading

Sheep, lupines, pattern, and process

Photo: Lupines below Öræfajökull, and sheep grazing at Sandfell, Iceland (S. Heard)

Last summer, we were driving around southern Iceland, admiring the fields of lupines (beautiful, even though they’re invasive) and the gamboling sheep (also invasive, at least to the extent they’re allowed to graze free). Before long, we noticed an interesting pattern: we saw dense fields of lupines, without sheep; and we saw thousands upon thousands of sheep, in fields without lupines – but we drove for days without ever seeing sheep and lupines together.

Being a nerd scientist, I came up with a hypothesis to explain this pattern: Continue reading