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Statisticians want to abandon science’s standard measure of ‘significance’

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Re: Statisticians want to abandon science’s standard measure of ‘significance’

#121

If you're looking for a replacement you don't understand the problem. The problem isn't that P=.05 is an arbitrary measure of significance. The problem is that only publishing significant results is a bias against the null hypothesis . Let's say you're doing a study of flipping coins. The null hypothesis is that the coin is evenly weighted. If the null hypothesis is true, when you flip a coin once, it will come up he…

Is there a compendium somewhere of null hypotheses as well as observed p values (or whatever statistic) for experiments with both "significant" and "insignificant" results? Depending on the phenomenon and the hypothesis, an event could have a different probability of occurring and require a different threshold. It seems like we are wasting a lot of effort when any experiment is unpublished, when we could at the least…

> It seems like we are wasting a lot of effort when any experiment is unpublished, when we could at the least be associating a data point with a particular hypothesis.

You're absolutely right, but journals don't see it that way. Journals want to make money, and the articles which make the most money are the ones that prove an alternative hypothesis. This is one of the ways where for-profit publishing is harmful for science.

> This would require some standardization of hypotheses, so that a researcher could select a hypothesis from a list, conduct an experiment to test it, and report those findings to some aggregator. Others would also test the hypothesis and report their findings. Eventually you have some distribution of findings that allow you to examine the experimental methods of outliers as well as modal experiments. In this way every scientific result is the product of some meta-analysis, rather than allowing a single custom experiment to produce a result.

"Standardization of hypotheses" gets a bit tricky and I suspect the standardization process would be stifling. Part of the goal of replication is to improve on methodology, and part of that is finding ways in which your hypothesis wasn't clearly defined, or doesn't contribute to a larger theory. There needs to be some flexibility in which hypotheses scientists pursue.

A more organic way might be for journals to categorize articles as testing new hypotheses or attempting to reproduce old results, and strive for some ratio between the two (1:4 or somesuch).

Re: Statisticians want to abandon science’s standard measure of ‘significance’

#122

Earlier quoted context omitted.

It seems like an education fail to me. Most people don't know the very basics of stats and we live in a world that's highly probabilistic. It seems like something that should be taught alongside math from elementary school, not something you can maybe get an elective in in high school or college.

> It seems like an education fail to me. I know a lot of people have trouble thinking clearly and correctly about probability and statistical inference. But do we know if, practically speaking, that can be addressed by a modified educational curriculum? Or are these concepts that would take an extraordinary amount of effort for many persons to understand well?

They're nuanced concepts that are easily misunderstood, but in a typical US public school, statistical significance (or anything beyond basic descriptive statistics) is not typically part of the curriculum[1]. It's a hard problem to effectively educate out of existence but right now we're not even really trying.

[1] source: I never saw it as a student, and I've consulted with math teachers (well, administrators, about math) in multiple states, and I've never had it come up there either.

Re: Statisticians want to abandon science’s standard measure of ‘significance’

#123

The problem isn't p-values, the problem is a binary distinction between p=0.049 and p=0.051. The problem would go away if everyone understood p-values, or we replaced use of the term "statistically significant" with "3% probability we're just seeing a pattern by accident". Renaming the term to something that sounds just as binary isn't any different.

I have a rule of thumb: Multiply p by 10. In other words, p = 0.05 is as good as a coin toss. This is consistent with the so called replication crisis.

In my view, understanding p-values won't help. Feeding data into a formula that produces a p-value doesn't account for things that can go wrong with experiments: Uncontrolled experimental conditions, biased sampling, hidden correlations, and simply non-ergodic systems. It is possible that some systems can't be controlled to the point where it's reasonable to start looking for real effects.

I suspect that if the results were any good, the precise interpretation of the p-value wouldn't matter. Physics has lived without an agreed-upon interpretation of quantum theory for a century.

Re: Statisticians want to abandon science’s standard measure of ‘significance’

#124

The problem isn't p-values, the problem is a binary distinction between p=0.049 and p=0.051. The problem would go away if everyone understood p-values, or we replaced use of the term "statistically significant" with "3% probability we're just seeing a pattern by accident". Renaming the term to something that sounds just as binary isn't any different.

I think this is part of the problem, but the more fundamental issue is that people are extremely bad about probabilistic reasoning. Even if we said "3% probability we're just seeing a pattern by accident" most people unconsciously round this down to zero.

People that work with computers often are slightly better about reasoning about probabilities because they often deal with high frequency events. A 1% error rate across 10 million events a day leads to 100,000 errors. If those events are transactions, payments, file uploads etc, a 1% chance starts to look very common. But even computer people are not immune to incorrectly reasoning about probabilities. I suspect there is some fundamental limitation at the cognitive level.

Re: Statisticians want to abandon science’s standard measure of ‘significance’

#125

Can someone help me understand the concern about p-value hacking? One of the comments below references this XKCD comic [0], which IIUC is an example of p-hacking. But in that comic, the only difference I notice between the original hypothesis (jelly beans cause acne) and the p-hacked hypothesis ( green jelly beans cause acne) is whether or not the hypothesis occurred to the researcher at the beginning of the study. A…

We already expect data to sometimes indicate significant evidence against the null hypothesis when the null hypothesis is actually correct. That's just the nature of the way we structure our statistics practices. But for each additional set of variables you have and could test for relationships, you increase your chances of finding a strong relationship that appears to be significant due to random chance, but was in fact not. (You may notice that this is just a different flavor of the issues that arise from the way researchers use significance tests).

The reason you need to pick your hypothesis ahead of time is because otherwise you may use intuition or just your eyeballs to find relationships in the data that are only there due to random chance. This will supposedly increase the probability of detecting spurious relationships and erroneously rejecting the null.

Re: Statisticians want to abandon science’s standard measure of ‘significance’

#126

The problem isn't p-values, the problem is a binary distinction between p=0.049 and p=0.051. The problem would go away if everyone understood p-values, or we replaced use of the term "statistically significant" with "3% probability we're just seeing a pattern by accident". Renaming the term to something that sounds just as binary isn't any different.

While I agree with that completely, the coinciding problem that I've run into time and time again is the temptation to accept statistical significance but ignore the size of the effect.

You might see p=0.00001 but if the size of the effect irrelevant, then the statistical significance of the relationship is still not something I care about. Great, orange juice shrinks tumors by 0.000001%. I'm still going with chemo, thanks.

Re: Statisticians want to abandon science’s standard measure of ‘significance’

#127

Earlier quoted context omitted.

It seems like an education fail to me. Most people don't know the very basics of stats and we live in a world that's highly probabilistic. It seems like something that should be taught alongside math from elementary school, not something you can maybe get an elective in in high school or college.

This guy is one of my favorite TED speakers, and he makes a strong argument for exactly this: https://www.ted.com/talks/arthur_benjamin_s_formula_for_chan... .

Thanks for sharing! (writes the girl who barely passed pre-calc)

Re: Statisticians want to abandon science’s standard measure of ‘significance’

#128

If you're looking for a replacement you don't understand the problem. The problem isn't that P=.05 is an arbitrary measure of significance. The problem is that only publishing significant results is a bias against the null hypothesis . Let's say you're doing a study of flipping coins. The null hypothesis is that the coin is evenly weighted. If the null hypothesis is true, when you flip a coin once, it will come up he…

This is an excellent write-up! Some friends of mine worked at one of the psychology departments as programmers/IT-guys while studying CS, lesson learned: Real knowledge of statistical methods is rare among psychology researchers; one (of my friends) even got fired because he pointed out that they asked him to fake results (the experiment basically assumed the Halting Problem to be solvable).

Re: Statisticians want to abandon science’s standard measure of ‘significance’

#129

Can someone help me understand the concern about p-value hacking? One of the comments below references this XKCD comic [0], which IIUC is an example of p-hacking. But in that comic, the only difference I notice between the original hypothesis (jelly beans cause acne) and the p-hacked hypothesis ( green jelly beans cause acne) is whether or not the hypothesis occurred to the researcher at the beginning of the study. A…

We already expect data to sometimes indicate significant evidence against the null hypothesis when the null hypothesis is actually correct. That's just the nature of the way we structure our statistics practices. But for each additional set of variables you have and could test for relationships, you increase your chances of finding a strong relationship that appears to be significant due to random chance, but was in…

Thanks, although I must admit I'm having some trouble following your logic.

IIUC, you're pointing out that when examining the empirical data gathered during an experiment, it's often possible to find some identifiable subset of the data that are consistent with a refined version of the original hypothesis. E.g., maybe jellybeans in general don't correlate with acne, but green ones do.

Assuming that the experiment is part of a larger effort to build or refine some model, I don't see the problem.

Suppose that someone refrained from p-hacking during the first run of that experiment. IIUC, they'd look at the experimental results, and wonder if they had missed some "X" factor. So they might conject that jellybean color was relevant, and rerun the experiment with the hypothesis, "consumption of jellybeans, but only of a particular color, correlates with acne." And (assuming sample sizes were big enough), the data gathered during that second experiment would likely confirm that green jellybeans correlate with acne.

But what's the point of having run that second experiment, when they could have just reached the same conclusion by testing additional hypotheses from the first experiment's data?

It seems like regardless of whether you just ran one experiment and did "p-hacking", or instead ran a follow-on experiment, you end up with the same refinements to the model you're working on.

Re: Statisticians want to abandon science’s standard measure of ‘significance’

#130

Earlier quoted context omitted.

This is actually a much better explanation of the problem than the main article. The main article kept saying that p values were not meant to be definitive, but without explaining what was wrong with them. At least, not very clearly. This comment is a much clearer explanation -- imho -- as to what goes wrong in the industry. I also think it is right to focus the attention away from a particular statistical measure.

It seems clear to me that the author just didn't understand the problem with P values. It's part of a larger problem of science journalism being done by journalists without scientific backgrounds. It's not their fault--even if you have natural ability and interest in both communication and discovery, it's hard to get an education in both. I have the opposite problem: my abilities lie more in the statistics/science th…

Let me check if I get it right: can this be said to be a case of incorrectly aggregating experiments? We're in a sense taking min(p) over all p-values, or any(significant) over all results, when we should use an aggregation method that takes into account the total number of studies aggregated?
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