It’s because I believe in percentages, not in probability. I took against probability on one of our family vacations to Maine, when we stopped in Washington D.C. on the way there to visit some friends. The newspaper was running an article, I remember, that said that one in ten black men in Washington D.C. had a criminal record, and I could not wrap my head around this.
“So if you take any ten black dudes from Washington D.C.,” I said, “one of them will always have a criminal record.”
“According to this article,” said my mother.
“But what if you happen to pick ten black men who are all not criminals?” I said.
“What if you flipped a coin twice, and it came up heads both times?” my mother pointed out. I think she was trying to demonstrate why my argument didn’t work against what the newspaper had said, but at the time I thought, oh my God, yeah, and that totally happens. And my belief in probability crumbled like badly-kneaded bread. Several years later when I read Rosencrantz and Guildenstern Are Dead, I was all like, Dudes, you are not special. Probability isn’t true and you just have to accept it.
I don’t have a problem with percentages. If I counted my books and found that 40% of them were hardback, I could accept that. But if I tried to tell myself that it was a four in ten chance any individual book I grabbed at random from my bookshelves would be a hardback, I would feel like I do when I try to trick myself into wanting to wash the dishes. Like, nice try, self. Next time, try bribing me with cookies.
I bring this up because my belief in percentages rather than probability has been causing me some trouble with weather forecasts. Every day before I go to work, I check the weather, and if it’s supposed to rain that day, I’ll take flip-flops and an umbrella, so my work shoes and purse (respectively) won’t get wet on the walk back from work.
The problem arises, I have realized lately, because when the weather forecast says 40% chance of rain, my brain interprets it to mean that if it does rain, and it might, the intensity of the rain will be 40% of the intensity that the sky could manage at full capacity. So I don’t bring my umbrella, because I don’t mind getting a little bit wet. Then it rains really hard, and it is like I have never heard of rain before, and I am outraged at the weather forecast for misleading me. As I try to figure out a way of walking that will keep me the most dry, I compose angry letters to the weather forecasters:
Dear Weather People,
I hate you. My purse is all wet and although I cannot look in a mirror until I get home, I suspect there is mascara dripping down my face. This is your fault for being a damn liar. It was not supposed to rain this hard today. Consider this letter a gauntlet slap in the face, and meet me on the green with pistols at dawn.
Hatefully,
Jenny
They never meet me on the green with pistols at dawn. That’s good because I am a terrible shot and would definitely lose.
The end.
Jenny's Books 
I have concluded that math is some sort of druidic rune system I can’t understand because it was created to repel the Normans and I’m French-American.
I wish I could use that excuse. I’m going to find a way to. That is fabulous.
Hahahah, I am partly French but mostly Irish, so if your theory is correct, that would make me even dumber. I prefer to pin it on that thing that makes girls stop liking math in middle school, which is exactly when I did stop liking math. THANKS A LOT MALE CHAUVINIST SOCIETY.
(See how I took my academic weakness and channeled it into outrage?)
LOL
You should read The Drunkard’s Walk; lots of fun stats. 🙂 I have a book about probability out from the library right now; I shall let you know if it’s any good!
The Drunkard’s Walk, you say? Is it about how it’s no use anyone bringing an umbrella anywhere because the weather people are just making stuff up? :p
I’ll look forward to seeing your review of the probability book! Maybe it will change my mind for me.
Probability is tough. I have to teach it this year in my math course and I struggle with it. I took a course in university and had no clue what was going on. The first time I taught this math course …ssh, I skipped that section and went right to statistics and bell curves, which are totally awesome. The last time I taught it, I got it! and probably didn’t explain it that great, but I’m pretty sure I got it. We’ll see how much has stuck with me. I guess my point is that even people who teach it find it tricky.
Plus, I totally bribe my self with treats to get the housework done.
Maybe I would understand it better if I had to teach it to someone. I used to practice for science and history tests by teaching all the material to my stuffed animals. :p
lol 😀 And lol again at Clare’s comment. I remember probabilities really clicking for me and suddenly making sense when I was taking a statistics class as a psychology major. Unfortunately, it’s been a long time and that particular insight is now gone 😛
I knew I should have taken statistics in college. My mother was always telling me to take a statistics class. But what happened was, I got to college and I found I deeply didn’t want to take a statistics class, and I took Cicero instead.
The thing is, you theory makes perfect sense..”The problem arises, I have realized lately, because when the weather forecast says 40% chance of rain, my brain interprets it to mean that if it does rain, and it might, the intensity of the rain will be 40% of the intensity that the sky could manage at full capacity…” I don’t understand how those weather people get paid the big bucks because most of the time they are wrong!
Thanks Jenny, you made me smile with all this numbers stuff. Have a great week.
I know! It makes perfect sense! And it’s often not that far from being true! That’s why it’s gained such traction in my brain.
You have a great week too! 🙂
Yeah, those dudes are not special at all.
The thing that got me was not cutting toenails. I don’t know what *your* toenails do when you don’t cut them, Rosencrantz (or Guildenstern), but I know where mine do, which is shred socks and collect lint. So that is just gross, and please don’t show me your feet.
Yeah! What on earth were they talking about? I am constantly getting out my nail clippers and I do fingers and toes both because if I didn’t unhappiness would result. Especially the kind where you are wearing pointy shoes and your pinky toe is all like STAB STAB STAB to your fourth toe. But I guess Rosencrantz and Guildenstern wear all square-toe shoes.
This post made me smile especially because it seems that lately whenever I leave work it is pouring down rain. This means that by the time I get the kids in the car from the sitters I am drenched. And it seriously seems to happen once a week. So I can just picture you mentally writing a letter to the weather person as I’ve done it myself a couple of times this past month 🙂
Poor you! What’s really a shame is that I love the rain as long as I am inside. If only the weathermen would arrange the rain to happen in the early morning and late evening, we could all be friends. :p
Too funny! I’ve noticed that it usually only rains if I wear my coat that doesn’t have a hood. Especially if I’m going somewhere where I actually care what I look like. This happened so many times last year (me with rain-flat hair at band practice especially) that I finally bought a pink umbrella and put it in the car. Pink because I have boys and none of them will take it that way.
Your umbrella strategy is very cunning. I do that at home, when I have my car–I keep an umbrella and a large blue poncho, so that I can wrap up books in the poncho and protect my hair with the umbrella. When I have no car it is harder.
Amen, sistah!
Yay! Support for my bad math skills makes me feel better about myself!
I actually laughed. ❤
I don't mind getting wet as long as I'm going somewhere with warm, dry clothes soon after. However, I'm fine with probability, or percentages. I actually grasp it better in probability form because… well… I do.
Damned if I know why.
I don’t mind getting me wet, but I have this massive purse that contains a lot of things I want dry, most notably the notebook in which I am writing a story every morning with my coffee. And my book, and my phone, and things. But it is lovely to come home all cold and damp and get in a hot shower and then put on warm pajamas.
I kind of wish it were winter…
I use waterproofing spray on all of my purses & bags. And most of my shoes, if they’re the sort that can’t/shouldn’t get wet and they have enough fabric that they’re worth waterproofing.
But then, most of my purses are ugly canvas/cotton, so it’s not like I’m messing up anything designer.
Lol. This is funny! When I check the weather forecast in the morning and it says there’s a less than 50 percent chance of rain and it’s sunny outside, I don’t bother to grab anything because I assume I’m above the rain. I should get over it 🙂
I should get over it too! But I am always weighing the chance of rain against the chance that I will have to haul my umbrella around all day in my already-quite-heavy purse.
I think I just tend to assume, without thinking about it, that if the percentage is above fifty it will rain, and if it’s below fifty it won’t. It makes no difference, though, because I live in Seattle and the rain here is pretty much always mist, so I don’t even own an umbrella.
I like a good dramatic thunderstorm myself. Whenever I’m in London, which tends toward misty rain, I like that it doesn’t storm and upset my plans; but I love sitting at home reading while it crashes thunder and pours down rain outside. (Unless the power goes off, hurricane-style. Then it gets far less fun.)
You are such a funny, funny writer. Here’s a good probability tale for you: Bill Bryson gets into the car of his brother-in-law, who’s agreed to give him a lift home. He notices a) a lottery ticket on the dashboard and b) that his b-i-l isn’t wearing a safety belt. ‘Do you know the likelihood of you actually winning anything on the lottery, compared to the likelihood of your death in a car crash?’ he asks him.
The brother-in-law gives him a look and says ‘And what do you think the chances are of me dropping you three miles short of home?’
Bill Bryson says he decided to keep his clever calculations to himself after that.
Hahaha, I love it. (My aunt won several thousand dollars with a lottery ticket once. It made me feel like winning was far more likely, even though that’s not how it really works.)
I have the same problem with the weather at times, and since I live in Florida, the probability of rain is always high. I usually just disregard this though, and always end up getting soaked on my afternoon walk with the dogs.
I guess I’m used to having a car. I need to adjust my brain. :p
this is a prime example of why i skulk about on your blog.
🙂
I love this post. I am also one of those folks who understand percentages pretty well, but just can’t get around probability. But never would I have been able to express myself so well.
I am going to show your blog post to my husband so that he can get that there are other people like me as well who end up getting wet in the rain using the same arguments like I do 🙂
Hi, Jenny!! This is my first time reading your blog. I stopped by for the DWJ week (OMG, LOVE HER!!) and read this post in the archives. I couldn’t help but comment~
I’ve noticed a LOT of people prefer percentages over probability… but personally, I think it’s because we’re not taught probability very well in school. The whole statistic of “1 in 10 black men having a criminal record” just means that IF you picked 10 black men in DC at random and checked their background (and did this an infinite number of times), and then took ALL the results, it’d average out to 1 in 10. (Or, they figured “Well, about this many black men live in DC… and about this many of them have a criminal record, giving us about 10%. 1 in 10.”). Same thing with the coin-flipping. The closer you get to doing it an infinite number of times, the closer you get to 50%.
But I do think it’s amazing how 10% and 1 in 10 are technically the same thing, but one just FEELS so much more reliable than the other! If you’re interested in a book that talks about the whole “math and why people hate it” thing, check out Innumeracy. It’s an easy read, but really interesting.
As for the weather thing, heehee. I can just imagine you getting soaked, wondering why this 40% rain has turned into a 90% deluge/soak-fest. “Weatherman, you LIE!” It’s just that when they look at the records of days that had the same atmospheric conditions, it rained on 40% of those days, so they consider it a 40% likelihood of rain.
Oh, the perils of probability and percentages.
(Also, SO EXCITED for DWJ week. SQUEE.)