Tag Archives: random

Data Tables: The scourge of falsely significant results #MRX

Histogram of sepal widths for Iris versicolor ...

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Who doesn’t have fond thoughts of 300 page data tabulation reports! Page after page of crosstab after crosstab, significance test after significance test. Oh, it’s a wonderful thing and it’s easy as pie (mmmm…. pie) to run your fingers down the rows and columns to identify all of the differences that are significant. This one is different from B, D, F, and G. That one is different from D, E, and H. Oh, the abundance of surprise findings! Continue reading →

5 random things about me

Inspired by @PeterFlom

1) In kindergarten, I won an award for having the quietest voice and the sweetest smile. I figure it was the teachers nice way of saying I need to speak up more. Or at least once.

2) I was hit in the head with an axe when I was ten years old. I didn’t feel any pain even though it gushed all over. I remember being worried that my mom would get me in trouble for misbehaving and for using up an entire box of kleenex to stop the blood. A hospital visit with needles and stitches ensued and all was fine. And how you ask? I was careless enough to walk behind my ten year old friend as he swung the axe over his head in preparation for a big swing forwards.

3) I am shy. People who I meet now don’t believe it but those who knew me before I was 20 can tell you. Couldn’t order food in a restaurant. Couldn’t purchase items in a store. Couldn’t smile at or say hi to someone passing in the hallway. When I hear shy people being called arrogant for not talking to people, it upsets me because I know the pain they are going through. I’m still shy but I work very hard to hide it. Sometimes I succeed. Please don’t point it out. You’ll only make it worse.

4) I would only have things that are pink if the world so produced and the people in it didn’t think I was utterly insane. Pink clothes, shoes, computers, houses, sugar.

5) I can gross people out by bending my thumb backwards. Did it work on you?

So who’s next?!

Common Mis-Numbers

English: Pi Pie, created at Delft University o...

Image via Wikipedia

Wouldn’t it be great it you could just read and interpret a number, and then be confident about your interpretation? If that was the case, you wouldn’t be able to buy 23 different books called “How to lie with statistics.”

Here are a few common problems I see when people try to interpret numbers.

Dislike matters just as much as like. Don’t get so focused on top box scores that you forget about bottom box scores. Brands can easily have identical top box scores and ridiculously different bottom scores.

How many times have you seen huge inexplicable spikes in your charts? Spikes are a key indicator that your sample size is too small. Be extremely nervous about numbers based on only 30 people. Be cautious of numbers based on fewer than 100 people. Check first and avoid embarrassing conclusions.

Everything on the planet is governed by rules. And one of those rules is randomness. When you’ve determined that a small sample size is not the cause of the spike, and there is no discernible explanation for the spike, consider that it may in fact be a random number. Random happens. Deal with it.

Just because a test came out significant today doesn’t mean it will with new data next week. See previous point. You will know you’ve really got something when its significant when it occurs on several unique occasions.

Happy Pi Day (to the 36th digit)!
Happy Pi Day (to the 36th digit)!‘ by Mykl Roventine via Flickr
Image is licenced under a Creative Commons Attribution licence

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