Necessary v. Sufficient: The Flash Mob Example

by Mary Richter Jun 14, 2012

My sister got married a month ago, and as the maid of honor, I saw it as my duty to do what any good maid of honor does: plan a flash mob for the reception.

I choreographed a routine to Maroon 5’s “Moves Like Jagger,” uploaded a humiliating instructional video onto YouTube (of yours truly doing the dance in my Brooklyn apartment), and spread the word (link). In the video, I say, “We want at least 40 people in the flash mob in order for it to look good. And if it has 50 or more, that’ll be amazing!”

Check out the sentences below. Based on what I’ve just told you, which statements are necessary? Which are sufficient?

	For it to be Good		For it to be Amazing
	Necessary?	Sufficient?	Necessary?	Sufficient?
1. At least 35 people participate in the flash mob.
2. At least 40 people participate in the flash mob.
3. Exactly 50 people participate in the flash mob.
4. No more than 40 people participate in the flash mob.

Answers:

1. Y, N, Y, N

2. Y, Y, Y, N

3. N, Y, N, Y

4. N, N, N, N

Want to see how the flash mob looked? Check out the video here!