628: Psychic

Explain xkcd: It's 'cause you're dumb.
Jump to: navigation, search
You can do a lot better than 1% if you start keeping track of the patterns in what numbers people pick.
Title text: You can do a lot better than 1% if you start keeping track of the patterns in what numbers people pick.

[edit] Explanation

A psychic is a person who claims to be able to access information that is beyond normal sensory perception through extrasensory perception. This information may vary widely in scope and value, ranging from archaeological to the ability to read minds. Cueball describes himself as such a person, to which Megan responds with disbelief because it is a bold and unsupported claim. To prove his abilities, Cueball has Megan think of a random number from 1 to 100, which he then guesses correctly to demonstrate his ability to read minds. Megan is amazed that Cueball was correct, but he simply dismisses her disbelief and wants to go back to pretending to lead a normal life.

The four panels are actually a setup to the real joke in this comic: the final sentence spoken by a narrator. It reveals that Cueball has simply played a trick on Megan and that anyone can repeat it. The joke is that, theoretically, a person can guess a random number from 1 to 100 once in one hundred tries, or 1% of the time, according to the law of large numbers. By playing this trick enough times on enough friends, the trickster is statistically likely to get a number right eventually. Assuming the person whose number he guesses is not familiar with the trick, it will appear as if the trickster is actually psychic. Should this happen, the trickster can then play the joke out as he wants, hence the "it's totally worth it" at the end.

The title text appeals again to statistics. People are poor random-number generators—e.g. being less likely to pick numbers at the extremes or exactly in the middle. Knowing this, the 'psychic' could restrict his guesses accordingly, improving his odds of guessing correctly.

[edit] Transcript

Cueball: I'm psychic, you know.
Megan: There's no such thing.
Cueball: Okay, think of a number from one to one hundred.
Megan: Okay.
Cueball: 43.
Megan: Holy shit!
Cueball: I try not to let it affect my life too much.
Megan: Wait, I can't believe this.
Cueball: Don't worry about it. Forget I said anything.
Megan: But-
Cueball: Let's get to the movie.
Megan: I, uh... Ok, sure.
This trick may only work 1% of the time, but when it does, it's totally worth it.
comment.png add a comment! ⋅ Icons-mini-action refresh blue.gif refresh comments!


Tip: No one picks 50. 01:35, 14 March 2013 (UTC)

The Answer to the Ultimate Question of Life, the Universe, and Everything is 42. This comic is wrong ;) --Dgbrt (talk) 18:52, 6 October 2013 (UTC)
Interestingly, it appears Megan was trying to trip Cueball up. The obvious choice would have been "42", a number with very geeky connotations, to say the least. Megan may have thought of it immediately, known Cueball would suspect, and gone for the next higher number, 43. Of course, Cueball was smart enough to realize this simple trick, and knew Megan was, too. So he won anyway. (talk) (please sign your comments with ~~~~)
Personal tools


It seems you are using noscript, which is stopping our project wonderful ads from working. Explain xkcd uses ads to pay for bandwidth, and we manually approve all our advertisers, and our ads are restricted to unobtrusive images and slow animated GIFs. If you found this site helpful, please consider whitelisting us.

Want to advertise with us, or donate to us with Paypal or Bitcoin?