Archive for June, 2018
Nationals Win Probability, and Other Meaningless Statistics
The first pitch of last night’s NationalsPhillies game was 8:08 p.m. That’s pretty late for me on a school night, and when a 38minute rain delay interrupted the 4th inning, well, that made a late night even later.
The Phillies scored 4 runs in the top of the 5th to take a 6‑2 lead. When the Nationals failed to score in the bottom of the 5th, I asked my friends, “What are the chances that the Nationals come back?” With only grunts in response and 10:43 glowing from the scoreboard, we decided to leave.
On the drive home, we listened as the Nationals scored 3 runs to bring it to 6‑5. That’s where the score stood in the middle of the 8th inning when I arrived home, and with the Nats only down by 1, I thought it might be worth tuning in.
The Nats then scored 3 runs in the bottom of the 8th to take an 86 lead. And that’s when an awesome stat flashed on the television screen:
Nats Win Probability
 Down 62 in the 6th: 6%
 Up 86 in the 8th: 93%
Seeing that statistic reminded me of a Dilbert cartoon from a quartercentury ago:
I often share Dogbert’s reaction to statistics that I read in the newspaper or hear on TV or — egad! — are sent to me via email.
I had this kind of reaction to the stat about the Nationals win probability.
For a weather forecast, a 20% chance of rain means it will rain on 20% of the days with exactly the same atmospheric conditions. Does the Nats 6% win probability mean that any team has a 6% chance of winning when they trail 62 in the 6th inning?
Or does it more specifically mean that the Nationals trailing 62 in the 6th inning to the Phillies would only win 1 out of 17 times?
Or is it far more specific still, meaning that this particular lineup of Nationals players playing against this particular lineup of Phillies players, late on a Sunday night at Nationals Stadium, during the last week of June, with 29,314 fans in attendance, with a 38minute rain delay in the 4th inning during which I consumed a soft pretzel and a beer… are those the right “atmospheric conditions” such that the Nats have a 6% chance of winning?
As it turns out, the win probability actually includes lots of factors: whether a team is home or away, inning, number of outs, which bases are occupied, and the score difference. It does not, however, take into account the cost or caloric content of my midgame snack.
A few other stupid statistics I’ve heard:
 Fifty percent of all people are below average.
 Everyone who has ever died has breathed oxygen.
 Of all car accidents in Canada, 0.3% involve a moose.
 Any time Detroit scores more than 100 points and holds the other team below 100 points, they almost always win.
Have you heard a dumb stat recently? Let us know in the comments.
How Would You Answer These Questions?
The following is one of my alltime favorite assessment items:
Which of the following is the best approximation for the volume of an ordinary chicken egg?

The reason it’s one of my favorites is simple: it made me think. Upon first look, I didn’t immediately know the answer, nor did I even know what problemsolving strategy I should use to attack it.
I used estimation, first assuming that the egg was spherical — and, no, that is not the start of a math joke — and then by attempting to inscribe the egg in a rectangular prism. Both of those methods gave different answers, though, and not just numerically; each led to a different letter choice from above.
Not satisfied, I then borrowed a method from Thomas Edison — I filled a measuring cup with 200 mL of water, retrieved an ordinary egg from my refrigerator, and dropped it into the cup. The water level rose by 36 mL. This proved unsatisfying, however, because although choice B is numerically closer to this estimate than choice C — only 29 mL less, compared to 34 mL more — it was five times as much as B but only half as much as C. For determining which is closer, should I use the difference or the ratio?
It was at this point that I decided the answer doesn’t matter. I had been doing some really fun math and employing lots of grey matter. I was thinking outside the box, except when I attempted to inscribed the egg in a rectangular prism and was literally thinking inside the box. And, I was having fun. What more could a boy ask for?
On a different note, here’s one of the worst assessment questions I’ve ever seen:
What is the value of x?
3 : 27 :: 4 : x
I can’t remember if it was a selectedresponse (nee, multiplechoice) item, or if was a constructedresponse question. Either way, it has issues, because there are multiple possible values of x that could be justified.
On the other hand, it’s a great question for the classroom, because students can select a variety of correct responses, as long as they can justify their answer.
The intended answer, I’m fairly certain, is x = 36. The analogy is meant as a proportion, and 3/27 = 4/36. (Wolfram Alpha agrees with this solution.)
But given the format, it could be read as “3 is to 27 as 4 is to x,” which leaves room for interpretation. Because 27 = 3^{3}, then perhaps the correct answer is 64 = 4^{3}.
Or perhaps the answer is x = 28, because 3 + 24 = 27, and 4 + 24 = 28.
Don’t like those alternate answers? Consider the following from Math Analogies, Level 1, a software package from The Critical Thinking Company that was reviewed at One Mama’s Journey.
If this analogy represents a proportion, then the correct answer is $10.50, but that’s not one of the choices. Instead, the analogy represents the rule “add $1,” and the intended answer choice is $10.00.
What amazing assessment items have you seen, of either the good or bad variety?
What Do They Think of RCV in Bah Hahba?
The Society of Actuaries does it.
Seventyfive percent of Great Britain — Scotland, Northern Ireland, and the United Kingdom — does it. (Fucking Wales.)
The Academy of Motion Picture Arts and Sciences does it.
And now Maine, the first state to implement a onetoone laptop program for all students, does it, too.
The “it” is rankedchoice voting, a method that allows voters to rank the candidates in their order of preference. When used to elect a single candidate, rankedchoice voting helps to select a winner that reflects the support of a majority of voters.
Many cities and towns already use rankedchoice voting to elect mayors and members of council. But Maine is the first state to use it for state and federal elections.
Many people, including Jennifer Lawrence, support rankedchoice voting. (That should mean something, right? After all, she’s the only person born in the 1990’s who’s won as Oscar. So far, anyway. Maybe she supports rankedchoice voting because the Academy used rankedchoice voting to award her an Oscar? Who knows.)
This video gives a very simple example of how rankedchoice voting works.
But maybe there’s a better example. Imagine that a book club is trying to decide which book they should read next, and rather than just voting for their top choice, the group instead ranks each of three books:
 Math Jokes 4 Mathy Folks (MJ4MF)
 The Grapes of Math (GM)
 Riot at the Calc Exam, and Other Mathematically Bent Stories (RCE)
The voting proceeds as follows:
Order  Number of Votes 
MJ4MF / Grapes / Riot  4 
MJ4MF / Riot / Grapes  5 
Grapes / MJ4MF / Riot 
6 
Grapes / Riot / MJ4MF 
2 
Riot / MJ4MF / Grapes 
2 
Riot / Grapes / MJ4MF 
1 
First, consider only the firstplace votes, and determine if any candidate received a majority. In this case, none of them received more than half of the firstplace votes: MJ4MF received 9 firstplace votes, Grapes received 8, and Riot received 3.
Since no one won, the candidate with the fewest firstplace votes is eliminated. Sorry, Colin Adams; we’ll have to say goodbye to Riot at the Calc Exam.
Now, the voters who had their first choice eliminated will have their votes counted for their second choice instead. So, 2 additional votes go to MJ4MF, while 1 vote goes to Grapes.
This means that MJ4MF, with 9 + 2 = 11 votes, is the winner, since Grapes received only 8 + 1 = 9 votes in the second round. Sorry, Greg Tang; you should’ve chosen a less worthy adversary.
C’mon, now… you didn’t really think MJ4MF was gonna lose, did ya?
On Tuesday, voters in Maine used rankedchoice voting to decide several political races, but they also got to vote on whether to use rankedchoice voting in future elections. Because rankedchoice voting takes time to tabulate, two of Tuesday’s contests were still undecided as of Thursday morning. So, voters literally were asked to decide if they should keep or reject a system that they had never seen used in an election. Doesn’t that seem just a bit odd?
You know what else is odd? Numbers that aren’t divisible by 2.