Dance p 3 Mar09

Dance of the p values, trial of 3 Mar 09

Category:

Science & Technology

Tags:

• Dance
• p
• 3
• Mar09projg

[geoffdcumming]

To dance with the p values yourself, go to website: thenewstatistics-dot-com and download ESCI ("ESS-key" Exploratory Software for Confidence Intervals), for Windows or Mac. Use the 'Dance p' page of the 'ESCI chapters 5-6' module. All free. Runs under Excel, simple to use.

That site also has info about my book:

Cumming, G. (2012). "Understanding The New Statistics: Effect Sizes, Confidence Intervals, and Meta-Analysis". New York: Routledge.

Enjoy!

Geoff

[Kalid0scop3]

Could you post your simulation program?

[geoffdcumming]

@Kalid0scop3 See comment I've just posted. There seems to be a block on stating a URL, so I had to omit the triple-w at the start and use the word 'dot', but I'm sure folks can figure it out. Enjoy. Geoff

[Komelsky]

Great, thank you!

The biggest problem with this example though (in my point of view) is that the N is inadequate to the effect size. Studying effects of this size with these typical N values is just insane! And that's even before considering how many variables - in a real experiment, in practice - you won't be able to control.

[geoffdcumming]

@Komelsky

Insane, yes, but typical for much published research in psychology and other disciplines. Cell biology routinely uses N=3! It is statistical power that determines the distribution of the p value. Power of only around .5 is typical of much published research. Crazy! Explore any other N, or power, using the Dance p simulation yourself--I've just posted a comment with details. Geoff

[ctwardy]

Good introduction to statistics, confidence intervals, and problems with P-values and null-hypothesis testing. Very well done -- Geoff put a lot of work into this.

[geoffdcumming]

@ctwardy

Hi Charles, Thanks! Yep, my first experiment with Camtasia. One day I'll do a super slick version. In the meantime I'm writing the book 'Introduction to The New Statistics: Effect Sizes, Confidence Intervals, and Meta-Analysis'. (Routledge, 2011),

Geoff

[theoldorganplayer]

great but i wonder rather than just showing histograms of the p values for various power levels would be good the show the actual distributions as you have in your excellent 2008 article, also I think you mention that when the null hypothesis is true the p distribution is uniform, just out of interest does the power level/effect size correspond to a parameter value for the p value distribution somehow?

[somerandomguyinshort]

I respect your effort, but I found it weirdly difficult to understand you - your voice sounded as if you were trying not to wake up the baby sleeping next door

[gracegirl04]

FANTASTIC!!! As an epidemiologist I say THANK YOU for educating people about the "sacredness" of the p-value from research

[mdoogue]

I enjoyed your Ockham's Razor and this is wonderf Geoff, thank you.

Matt Doogue

[drflynn73]

What's that tune? I'm sure I've heard it somewhere.