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Pre-Algebra: Sampling Methods 1865 Views


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If you're looking for tips on how to score more free samples at Yogurtland, you've got the wrong video.

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Transcript

00:04

Sampling Methods, a la Shmoop.

00:06

Ten days after setting sail from London with his…questionably hygienic…crew… [Captain Cornelius with his crew on a ship]

00:11

…Captain Cornelius discovered a parchment, reading:

00:14

"On the next full moon, Cornelius sleeps with the fish."

00:21

… Captain Cornelius created a poll to see if the crew was planning a mutiny. [Cornelius designing a poll on a parchment]

00:26

He spent the better part of a month pondering the benefits of random sampling versus stratified sampling.

00:32

In random sampling, the polltakers would be chosen at random… [A roulette wheel spinning]

00:35

…each sample having an equal chance of being chosen.

00:39

However, the Captain Cornelius remembered that 20% of the crew were British royal navy men…

00:44

… while 80% of the crew were pirates. [A UK flag and a Pirate flag on the ship]

00:47

This seemed like some important information about the crew’s subpopulations, or strata.

00:53

In a stratified sampling, 20% of the polltakers would be made up of navy men while

00:58

80% would be pirates.

01:00

By taking samples proportionate to the crew’s subpopulations…

01:05

…the likelihood of accurate information is increased. [Cornelius swimming with sharks]

01:08

Well of course, he could have also used Systematic Sampling…

01:12

…where he might have lined up all 300 crew members and then just polled every tenth guy

01:17

to get a 10% sample. [Crew of men selected in systematic sampling]

01:19

Or he could have used Convenience Sampling, where the captain would have

01:23

simply polled those crew members who were within shouting distance… [Cornelius shouting and crew members appear]

01:26

…so he wouldn’t even have to get out of bed.

01:28

But he knew that stratified sampling would be the best option here...

01:31

…because he knew certain characteristics about the crew that could change

01:35

the results if the poll were conducted in a different way.

01:39

In the end, Captain Cornelius succeeded in collecting conclusive evidence that a mutiny [Cornelius walking the plank on the ship]

01:44

was indeed being planned.

01:45

Maybe he’ll be able to share the results of his poll with Davy Jones. [Cornelius thrown off the plank into the sea]

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