Posts from November 2017 (14)

Each week, we would like to invite readers of Stats Chat to submit nominations for our Stat of the Week competition and be in with the chance to win an iTunes voucher.

Here’s how it works:

• Anyone may add a comment on this post to nominate their Stat of the Week candidate before midday Friday November 10 2017.
• Statistics can be bad, exemplary or fascinating.
• The statistic must be in the NZ media during the period of November 4 – 10 2017 inclusive.
• Quote the statistic, when and where it was published and tell us why it should be our Stat of the Week.

Next Monday at midday we’ll announce the winner of this week’s Stat of the Week competition, and start a new one.

(more…)

If you’d like to comment on or debate any of this week’s Stat of the Week nominations, please do so below!

Seeing a headline like

might cause an unwary person to think that eating purple kumara would reduce their risk of colon cancer by seventy-five per cent.

You, of course, would be suspicious and would want to read the story.

He found that when fed to three generations of mice bred with colon cancer, using the same gene which caused the disease in humans, purple kumara reduced the number of polyps by two-thirds or more.

So, the study is in mice. Mutant mice.  And it didn’t reduce the risk of colon cancer in these mice — which was basically 100% — it reduced the number of developing tumours.

It’s true that the mutation is one that occurs in people, too. About one in ten thousand people is born with the mutation that the mice had — these people have the mutation in every cell in their bodies, and they all get colon cancer if they don’t have major surgery.  And in the majority of ordinary people who get colon cancer, part of the  process is a mutation in this same gene in one cell.  So, the mutant mice are relevant.  There isn’t any problem with the research being in mice, just with the headline. Especially as further down in the story we hear about the equivalent dose of kumara in humans

“To eat 1kg of sweet potato every day is too hard.”

and that the kumara seems to have most potential as a way to produce a concentrated extract.

So far, there’s not much evidence either way on whether anthocyanins (basically, purple food other than beets or dragonfruit) really prevent cancer in humans.  Animal studies such as this one give good reasons to be hopeful; the history of other micronutrient-based prevention trials give good reasons to be skeptical.

From the MetService rain radar

If the band of rain were moving north-east, small uncertainties in its motion and orientation would mean that you’d know there would be half an hour of rain in Auckland, but not exactly when.

If it were moving south-east (as it is), small uncertainties in the motion and orientation mean that you know it will rain for a long time somewhere, but not exactly where.

One way to communicate the difference between these two predictions would be to show a set of possible realisations of rainfall.  For NW movement, you’d get a set of curves each with a single hump but at different times. For SW movement you’d get a much wider range of curves, where some showed no rain and others showed half a day or all day. I don’t know enough about ensemble forecasting to be sure, but I think this would be feasible

In principle, the common ‘patchy torrential downpours’ Spring rain pattern would show as rain curves each with different short periods of rain. I don’t think the technology is up to that using genuine predictions, but it might be possible to predict that we’re going to get that sort of weather and simulate the ensemble curves.

Current forecast summaries are mostly (except for hurricane paths) about averages: the probability of rain,  the expected amount, the worst-case amount. As technology progresses we will increasingly be able to do better than averages.