ShmoopTube

Where Monty Python meets your 10th grade teacher.

Search Thousands of Shmoop Videos

And vs. Or Probability 26622 Views

Share It!

Description:

Introducing And vs. Or Probability. Always remember that AND equals multiplication because it's the chance of both events happening, and OR means addition because it means one OR both events happening. What's the probability of us finally moving out of our mom's basement this weekend? Don't answer that.

Language:

English Language

Subjects:

Probability / Probability

Common Core Standards:

Transcript

00:04
And versus Or Probability, a la Shmoop.
00:07
Fred the Sock Monkey’s been pretty down lately. [Fred covering his eyes with his hands]
00:10
It’s taking him a while to get over his wedding day, when Dogzilla ate his fiancée. [Dog eating Fred's fiancee]
00:15
Finally, the day comes when Little Sally opens her sock drawer, which can only mean one thing…
00:20
She’s going to make a new sock monkey! It would rock Fred’s actual socks if the new

00:26
Lady Monkey was green or blue. [Fred with a green and blue sock monkey]
00:28
Sally’s drawer contains 3 orange socks, 5 green socks, and 4 blue socks.
00:35
If Sally blindly reaches into her drawer and pulls out one sock… [Sally pulls out sock from drawer]
00:39
…what are the chances of her pulling out a green OR a blue sock?
00:44
The phrase “what are the chances” probably means this is a probability question.
00:50
Probability equals “The Number of Ways an Event Can Occur” divided by “The Total
00:56
Number of Possible Outcomes.” [Probability definition]
00:58
Sally is going to pull out one sock…
01:00
…so our probability is the number of Blue and Green socks over the total number of socks.
01:06
By counting the socks… [Green, orange and blue socks in Sally's drawer]
01:08
…we discover the number of Blue and Green socks is 9, and the total number of socks
01:12
is 12.
01:13
So P equals 9 over twelve, which simplified is 3 over 4…
01:18
… which, when expressed as a percentage, is 75%.
01:22
Fred is a curious little monkey… …so he also wants to know… what is the
01:26
probability of pulling out a sock that is neither blue NOR orange?
01:32
Since there are 5 socks that are neither blue nor orange… they’re all green, by the
01:36
way... …we know that the probability will be 5
01:39
over the total number of socks, which is 12. Or about 41.6 %. [Probability of green sock chosen]
01:43
But Fred’s just happy that there is a 75% chance of having a blue or green lady monkey…
01:49
… and he can spend hours staring longingly into her buttons…[Sally appears with blue sock monkey for Fred]
Full Transcript