1. Do now: Identify the population and sample
A furniture maker buys hardwood in batches. The supplier is supposed to dry the wood before shipping (wood that isn’t dry won’t hold its size and shape. The furniture make chooses fine pieces of wood from each batch and tests their moisture content. If any pieces exceeds 12% moisture content, the entire batch is sent back.
Each week the Gallup Poll questions a sample of about 1500 adult U.S. residents to determine national opinion on a wide variety of issues.

2. Do you have any questions?

3. Poster Activity

4. Observation study or Experiment
Shout Key: to

5. Collecting Data-Sampling
Module 5

6. Sampling Plan Describes exactly how we will choose the sample
A sampling plan is biased if it favors certain outcomes.

7. How to sample badly Sample Badly with Volunteers:
In a voluntary response sample, a large group of individuals is invited to respond, and all who do respond are counted.
Voluntary response samples are almost always biased, and so conclusions drawn from them are almost always wrong.
Voluntary response samples are often biased toward those with strong opinions or those who are strongly motivated.
Since the sample is not representative, the resulting voluntary response bias invalidates the survey.

8. How to sample badly Sample Badly, but Conveniently:
In convenience sampling, we simply include the individuals who are convenient.
Unfortunately, this group may not be representative of the population.
Since the sample is not representative, the resulting convenience sampling bias invalidates the survey.

9. Observation study or Experiment
Shout Key:
repeat

10. How do you eliminate bias?
Random Sampling: Everyone in the population has an equal chance of being selected.

11. How does this work?
Let’s take a look at the Gettysburg Address…

12. Observation study or Experiment
Shout Key:
been

13. Exit Ticket
What are the differences between the 2-ways to sample badly?
Why is it important to have a random sample?