Monday, December 10, 2007

Null hypothesis.

That's fine, except for the fact that some aura readers believe that everything has an aura. That, in itself is not a tight enough question.

If they claim everything has an aura, then there's nothing to test. I'd recommend a good optician because that sounds more like a sight defect than anything else.

It's all academic, since I don't study auras so won't be doing the tests. Let's deal with the other argument here.

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This is a separate argument, by the way, on a non-paranormal subject. Nothing to do with any other argument. This argument is about the application of the null hypothesis in a scientific format and does not reflect on any points anyone has raised in any other argument.

On the 'null hypothesis', it's a common error to assume it has an overall applicability to a subject. It has a specific applicability to individual experiments.

No appeal to authority, no argument ad hominem, no 'style over substance'. The latter applies when someone tries to shoot down your argument by emphasising, say, a misspelling or the wrong use of a word or term. I haven't tried to shoot down Dikkii's argument, in fact we can agree that auras are unproven and the ability to see them, if it exists, is difficult to test. The only argument I see here is that he doesn't think it's worth trying, while I think it might be. Since I'm not planning to try, and neither is he, there's not even much of an argument at all.

I don't even have a claim to defend with those buzzword structures. All I was doing was trying to correct a common misconception about a specific component of any scientific experiment. Call it a hangover from my lecturer days, but I don't like to see incorrect interpretations of scientific terminology.

So, Dikkii, let me try again. If you have a hair you found in an area where Bigfoot is sighted, you can test it. Your null hypothesis for that test is 'the hair is from a known species'. With that in mind, you test it against every species known. Not just those indiginous to the area, because someone might have released a pet, or the hair could have been planted by a fraudster. Your null hypothesis holds true until you are certain the hair does not belong to a known species. If you find a match, the null hypothesis is proven. End of experiment.

However, 'bigfoot doesn't exist' sounds like a null hypothesis, but it isn't because there's no specific experiment to test it. 'Bigfoot doesnt exist' and 'Bigfoot exists' are, at this stage, opinions.
Better yet, let's make it 'ghosts' (because we're both of the opinion Bigfoot isn't real so we'd have nothing to argue about).

Now, your opinion is 'ghosts don't exist', mine is 'they do'. I can't prove they do, and I don't have a clear experimental protocol which would lead me to produce such proof. Likewise, you can't prove they don't - and you don't have an experimental protocol to prove that either. So neither of us can formulate a null hypothesis.

If we visit a specific site, where a haunting is claimed, then we can formulate a null hypothesis. We would both arrive at the same one, which is 'any physical effects observed have a non-paranormal explanation'.

Say the lights are flickering. Change the lightswitch, it stops. Null hypothesis proved for that case.

Scratching in the walls, accompanied by evidence of rodent infestation. Null hypothesis proved again.

Feelings of unease, shapes glimpsed from the corner of the eye - look for low frequency vibrations. Turn off the source, and if the symptoms vanish, the null hypothesis wins again.

In any such investigation, of course, the null hypothesis cannot be broken unless a ghost actually appears. In the absence of such an event, the investigation concludes 'no detectable physical explanation', but the null hypothesis is intact. The site remains of interest because the experiment was not concluded one way or the other.

Back to the bigfoot hair - again, the null hypothesis cannot be broken here because even if you don't find a match, it might be another unidentified species. No match doesn't prove it's bigfoot. However, if it's an unidentified species you can bet zoologists will carry on looking for that species, whether it's a bigfoot or a new kind of shrew.

That's how the null hypothesis works. I wasn't intending to 'have a go' at you, just correcting erroneous usage. It's a public blog, and if I let it go (and thereby tacitly agree to that usage) then my scientific credentials take a dent. It certainly wasn't any attempt to shoot you down by means of a personal attack.

I'm curious as to why, if it's not standard "use of jargon", as you describe it, you would imply that a scientist's comprehension skills are so deficient that they wouldn't be able to decipher such a simple statement?

Nobody would have any trouble working out what you meant, but what you meant wasn't a null hypothesis.

In any event, a quick search on Google brings up 18,700 hits for "assuming the null hypothesis" in quotes.

Not that many, considering there are far more than 18,700 scientists in the world. Also, it's such a common error that I'd have expected far more. Bad argument, and an appeal to Google's authority, perhaps? A good scientific/statistical textbook might be a better choice.

I would suggest that you steer clear of arguments such as these.

I never steer clear of arguments. Sometimes I start them just for fun.

You're just simply incorrect, is all.

Not this time. The null hypothesis has a specific application. It must be directly testable in an experimental format. It is not just a fancy way to say 'no it isn't'. I could direct you to a university statistics department website or two, or even Wikipedia's entry, but you'd just call that an 'appeal to authority' and ignore it. For anyone who does want to check up on me, the search term to use is 'null hypothesis definition'.

I've restricted this post to a discussion of the null hypothesis, and separated it from any other paranormal discussion so that it can't come across to anyone as if I'm trying to break an argument with semantics. In fact, I will state now that discussing the use of this term has no bearing on any of the points Dikkii has raised and is not at all a part of the arguments we are having now, or might (probably will) have in the future. This is an entirely separate argument.

11 comments:

Dikkii said...
This comment has been removed by the author.
Dikkii said...

Whoops, meant to press preview. I'll have the real deal up in a moment.

Dikkii said...

Nope. Lost it for good. I'll have to type it again. Apologies, Romulus.

Dikkii said...

OK. Null hypothesis. I did write a detailed comment on this, but I am a goose who lost it because I hit the wrong button. So I'll attempt to type it again.

Call it a hangover from my lecturer days, but I don't like to see incorrect interpretations of scientific terminology.

Oh boy. You're not going to like this one then.

However, 'bigfoot doesn't exist' sounds like a null hypothesis, but it isn't because there's no specific experiment to test it.

That's incorrect because we don't test the null hypothesis. We test the extraordinary claim.

And where evidence is not found for the extraordinary claim, we continue to assume the null hypothesis. Which is not so much that "Bigfoot doesn't exist." It's better worded as "There is no evidence to support the existence of Bigfoot."

Or, to put that another way, (because you don't like my terminology, natch) the null hypothesis is the default position.

Now, you don't like my Bigfoot "null hypothesis" and you wouldn't agree that if I used the word "Ghosts" instead things would be any different.

So let's go for the big one.

God.

Richard Dawkins used the term "The God Hypothesis" a couple of years ago in his book "The God Delusion" to describe the notion that God (or gods) exists.

Dawkins also, throughout the aforementioned book, refers to the alternate position as the "null hypothesis".

In other words, the null hypothesis to Dawkins God Hypothesis (i.e. the extraordinary claim) is this:

"There is no evidence to support the existence of god(s)."

Now it is sounding like an "appeal to authority" right now. However, that's not the point. What is the point is this:

There is no evidence that I can find that suggests broad disagreement with Dawkins use of the terminology from scientists or science historian-philosophers.

Here's a test for you. You used to be a lecturer, so you should have contacts at the university where you used to work. Make an appointment with any academic within the HPS department and ask them these two questions.

1. Is it correct to assume the null hypothesis where no evidence exists to support a particular claim?

2. Was Richard Dawkins correct in referring to the God hypothesis as an "hypothesis"?

3. Would "there is no evidence to support the existence of god(s)" be considered the resulting null hypothesis?

If the answers aren't "yes", a qualified "yes" and "yes" I will be very surprised.

I could direct you to a university statistics department website or two, or even Wikipedia's entry, but you'd just call that an 'appeal to authority' and ignore it.

Not this time. Your references are both relevant, and are not red herrings. I referred extensively to Wikipedia and my rather tattered copy of Karl Popper's The Logic of Scientific Discovery while typing this post. I also emailed one of my old school mates who still lectures a bit. Have you read Popper's book? It was one of my textbooks for HPS when I studied it.

You raised several questions which I would like to ask, but I will keep this on topic. Specifically about extraordinary claims, Popperian falsifiability, parsimony and your knowledge of Occam's Razor. Some other time perhaps.

Romulus Crowe said...

Be surprised. Be very surprised.

1. Is it correct to assume the null hypothesis where no evidence exists to support a particular claim?

No. If there is no evidence at all to support a claim, then there is nothing to investigate. You don't 'assume the null hypothesis', you don't set up an investigation. You tell the claimant to come back when they have something you can test. If they do, then you can formulate hypotheses.

2. Was Richard Dawkins correct in referring to the God hypothesis as an "hypothesis"?

I haven't read his book so can't say. It depends how it was worded.

3. Would "there is no evidence to support the existence of god(s)" be considered the resulting null hypothesis?

No. I covered that in my last response. That sentence constitutes a fact, not a hypothesis. That there is no evidence is not disputable. There is none. Therefore it's not testable, and therefore not a hypothesis.

Make an appointment with any academic within the HPS department and ask them these two questions.

I suggest you try it at a statistics department, as well as history and philosophy of science. The null hypothesis originated with the statisticians, not the historians.

I don't think any of the universities where I currently have contacts even have a HPS department. The only one I can think of is at Cambridge. I'll see if there's a nearer one, and who they've got who's up for an argument.

Romulus Crowe said...

That's incorrect because we don't test the null hypothesis. We test the extraordinary claim.

Huh? In your last post, you berated me repeatedly for not testing the null hypothesis, to which I've already replied. The hypothesis is the test, not the thing being tested.

Oh, Blogger loses posts for me all the time. For long ones, I now write them in Word and paste them in from there. It saves me banging my head on the desk so often.

Dikkii said...

Huh? In your last post, you berated me repeatedly for not testing the null hypothesis, to which I've already replied. The hypothesis is the test, not the thing being tested.

I'm looking everywhere but I can't find this particular quote of mine. Could you put it up for me?

Incidentally, I've only just twigged that you only tolerate the term "null hypothesis" in it's narrow application to the statistical method and not its broader use.

I have to admit that you've thrown me here - I remember very little about the statistical method and exactly how the "null hypothesis" is tested, statistics wise.

Going to have to re-visit my old statistics textbooks. And also find an acceptable term for "null hypothesis" that means "default position" that'll be acceptable to you, otherwise this is going nowhere.

Romulus Crowe said...

We could just agree to not use the term. For the sake of the non-technical who visit, perhaps 'not proven' or 'no evidence for' would do? It's occurred to me that most people don't see what the heck we're fighting about.

Then, we'll no doubt find some other term to argue about.

Romulus Crowe said...

I'm looking everywhere but I can't find this particular quote of mine. Could you put it up for me?

Here's one where you tell me I'm going about things the wrong way because I'm not testing the null hypothesis, but testing the alternate hypothesis (what I believe you refer to as the 'extraordinary claim')


Your ghost example is a good one for that. But you went about this the wrong way.In your example, you are not testing for the null hypothesis at all. You are testing other possible explanations (hypotheses, even) by a filtering process in order to be able to say, "Looked for rodents - couldn't find evidence for them. Looked for flickering lights - couldn't find evidence for them."

By the way, your last two lines are the wrong way round. I don't look for rodents unless I suspect them as a potential explanation - for a scratching in the walls, for example. No evidence of rodents doesn't mean 'no rodents', it just means I didn't find any. I'd have to take the house apart to be certain. The flickering lights are a symptom, not something to look for.

There was an especially interesting one involving a scratching in the ceiling. I should post that one, one day. It wasn't a ghost.

Dikkii said...

Aw nuts. I thought I'd posted a comment in here. I'll have to do this again. Blogger is really irritating me at the moment.

The quote you provided is a little of my poor wording, bad typing and a little out of context.

By the way, I recall typing this, but I can't find it anywhere on your blog. Do you have the comment permalink by any chance?

The comment was actually a response to something else you'd written, and given that I think we've agreed to restrict usage of the term "null hypothesis" to its statistical context, it's probably better written as this:

Your ghost example is a good one for that. But you went about this the wrong way.In your example, you [deleted]are not testing for the null hypothesis at all. You[/deleted] are testing other possible explanations (hypotheses, even) by a filtering process in order to be able to say, "Looked for rodents - couldn't find evidence for them. Looked for flickering lights - couldn't find evidence for them."

By the way, I meant to post the flickering lights and the rodents in the same order that you put them in your post. I mucked it up. Apologies.

There was an especially interesting one involving a scratching in the ceiling. I should post that one, one day. It wasn't a ghost.

Normally, that would be possums down our way.

Romulus Crowe said...

Wording is important because we're not having a private conversation. Anyone can read this - so if I read it as I did, others might too.

If this was a private conversation, much of these 'aside' arguments would never occur. Details can be overloked in a private conversation because they don't matter. Nobody else is listening.

That's the only reason to pick up on these details.

I think the original post was under 'Considering auras', but haven't looked yet. I'll check.

It was birds, with an unusual form of roof insulation. I've been considering a post on what a paranormal investigator really has to do, which might put off a few of the 'weekend woos' (if I can steal a bit of skeptic terminology for a moment).

Seriously, they do hinder research. I've seen a change in attitude from 'Really? A paranormal investigator?' to 'Oh, no, not another spook-chaser' since TV caught on to the thing.

I don't blame them for being interested, but I do blame them for not taking the subject seriously.

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