Monday, June 27, 2016

Curry Free Throws vs Suspected Terrorist Gun Buys

A comparison by Zachary Crockett from Vox: a suspected terrorist can buy a gun more easily than Steph Curry can make a free throw. Via Visual News.

Monday, June 20, 2016

Remembering Orlando

Orlando is reeling. Here it is in more tranquil times: Lake Eola Park downtown, the site of many vigils this past week.

Brian Resnick and Javier Zarracina from Vox have a cartoon explaining mathematically that predicting a mass shooting, like Pulse, is beyond our abilities. They consider a prediction that is 99% accurate in detecting a lone mass shooter. That shooter, hiding within a group of 1000 people, could be labeled by such a prediction, but that same prediction could label another 9 law abiding folks as potential threats.
If such a prediction scheme was used for the the 323 million people of the US, we could have a false positive group of over 3.2 million!

Monday, June 6, 2016

On The Road ... Map

On a trip to visit family, we stopped at a gas station in Hammondville, Alabama. On the wall was a map of the US with this wear pattern of customers touching where they were on the map. The many touchers have worn though the paper map down to the underlying supporting board. It seems that many have traced their path of travel extending southwest to Birmingham, AL and northwest to Chattanooga, TN likely along the connecting route US 11, passing through Hammondville, or along the parallel interstate 59 a bit further west. What remains is a roughly ellipsoidal bivariate frequency distribution of wear with a greater frequency of wear centered on Hammondville and lesser frequencies of wear in ellipsoidal contours around it.

Monday, May 30, 2016

Is 2 better than 1?

Not a statistical image this time, but a scene from the espionage novel "The Gun Seller" by writer, actor, musician Hugh Laurie. He uses an old example with a misunderstanding of the probability of joint events. Consider two events B1 an B2 each occurring with the same probability P(B1) = P(B2) = p. If they occur together, their joint probability is denoted P(B1 and B2). We can think sequentially and consider
P(B1 and B2) = P(B1)P(B2 given B1) and if they are independent 
P(B2 given B1) = P(B2) = p. So that under independence 
P(B1 and B2) = p2 , much smaller than p. Notice how he relates this below. 

There was a bomb scare on the flight out to Prague. No bomb, but lots of scare.We were just settling ourselves into our seats when the pilot’s voice came over theintercom, telling us to deplane with all possible speed. No ‘ladies and gentlemen, on behalf of British Airways,’ or anything like that. Just get off the plane now.
We hung around in a lilac-painted room, with ten fewer chairs than there were passengers and no music to play by, and you weren’t allowed to smoke. I was, though. A uniformed woman with a lot of make-up told me to put it out, but I explained that I was asthmatic and the cigarette was a herbal dilation remedy I had to take whenever I was under stress. Everybody hated me for that, the smokers even more than the non-smokers.When we finally shuffled back on to the aircraft, we all looked under our seats, worriedthat the sniffer dog might have had a cold that day, and that somewhere there was a little black hold-all that all the searchers had missed.  
There once was a man who went to see a psychiatrist, crippled by a fear of flying. His phobia was based on the belief that there would be a bomb on any plane he boarded. The psychiatrist tried to shift the phobia but couldn’t, so he sent his patient to a statistician. The statistician prodded a calculator and informed the man that the odds against there being a bomb on board the next flight he took were half a million to one. The man still wasn’t happy, and sat there convinced that he’d be on that one plane out of half a million. So the statistician prodded the calculator again and said ‘all right, would you feel safer if the odds were ten million to one against?’ The man said, yes, of course he would. So the statistician said ‘the odds against there being two, separate, unrelated bombs on board your next flight are exactly ten million to one against.’ The man looked puzzled, and said ‘that’s all well and good, but how does it help me?’ The statistician replied: ‘It’s very simple. You take a bomb on board with you.'
I told this to a grey-suited businessman from Leicester, sitting in the seat next to me, but he didn’t laugh at all. Instead, he called a stewardess and said he thought I had a bomb in my luggage. I had to tell the story again to the stewardess, and a third time to the co-pilot who came back and squatted at my feet with a scowl on his face. I’m never going to make polite conversation ever again. 
Perhaps I’d misjudged how people feel about bombs on aeroplanes. That’s possible. A more likely explanation is that I was the only person on the flight who knew where the hoax bomb call had come from, and what it meant.
 Of course no statistician would suggest such an action. Comic irony or real misunderstanding?

Monday, May 16, 2016

So Young, So Old

Nathan Yau at Flowing Data has produced an interactive graphic to compare your age with others. What percentage of the US population is younger than you? What percentage is older? In the static image above the US median age appears to be about 37 years old. Based on a 5-year American Community Survey from 2014, his interactive graphs lets you slide the line to match any age and see the percentage of Americans older or younger.