Bias and Unbiased Samples

To get valid results, a sample must be...

• biased

• unbiased

Simple random sample and systematic random sample are two types of ...

• biased samples

• unbiased samples

Convenience sample and voluntary response sample are types of...

• biased samples

• unbiased samples

To determine if my students like Math, I surveyed every 3rd student that walked into my classroom. This is an example of a ...

• simple random sample

• systematic random sample

• convenience sample

• voluntary response sample

To determine how many students at Shull would attend the dance, the principal surveyed the students in Ms. Miller's math class. 10 students said they would attend and 15 said they would not attend. It can be concluded that half the students at Shull will attend the dance. Is this conclusion valid? Why or why not?

• Yes, this is a simple random sample. So the sample is unbiased.

• No, this is a convenience sample. So the sample is unbiased.

• No, this is a voluntary response sample. So the sample is biased.

• No, this is a convenience sample. So the sample is biased.

The Student Council asked every tenth student in the lunch line how they preferred to be contacted with school news. The results are shown in the table. Is this an unbiased sample? If yes, suppose there are 684 students at the school. How many can be expected to prefer E-mail?

• No, it's a biased sample

• 432

• 304

• 16

A sample should be

• representative of  only middle school students only
• a very large group
• representative of the population
• representative of people who volunteer

Determine if the conclusion is valid.

A random sample of people at the mall shows that 22 prefer to take a family trip by car, 18 prefer to travel by plane, and 4 prefer to travel by bus. Is this sample method valid? If so, how many people out of 500 would you expect to say they prefer to travel by plane?

Bus = 9%

Plane = 41%

Car = 50%

• The conclusion is valid, about 200 people

• The conclusion is not valid

• The conclusion is valid, about 205 people

• The conclusion is valid, about 250 people