Sampling and Bias

The population describes:

• The group of people, objects or events being surveyed
• a part of the group being surveyed
• the whole world
• the school

Tags

CCSS.7.SP.A.1

CCSS.HSS.IC.A.1

The sample describes:

• The group of people, objects or events being surveyed
• a part of the group being surveyed
• the whole world
• the school

Tags

CCSS.7.SP.A.1

CCSS.HSS.IC.A.1

Why do we use sampling?

• Often, the population is so large that surveying or measuring all is expensive or impossible.

• Sampling is not used in statistical studies.

Tags

CCSS.7.SP.A.1

CCSS.HSS.IC.A.1

Why do we randomly select our samples?

• for control
• reduce bias
• so we don't get the same answers from everyone
• to eliminate confounding results

Tags

CCSS.HSS.IC.B.3

Why must a sample be unbiased and random? There are TWO correct answers.

• So you can be sure that no population subgroups are purposefully left out, thereby skewing results

• It is not important to give each person or studied measure a fair chance of selection in sampling.

• A random sample means that each member of the population has a fair chance of selection.

• Samples do not need to be unbiased--you should select a group for the results you want.

Tags

CCSS.HSS.IC.B.3

Dylan wants to know how the students at his school rate the cafeteria.  He surveyed his school's basketball team to rate the school cafeteria. Is this a biased sample of the school's population?

• Yes, because it is a convenience sample. The sample is asking a very specific group that will not accurately match the population.

• No, the basketball team has the smartest students and best athletes.

• Yes, because it's voluntary survey that only interested students took.

• No, he should have asked the football team since football players eat more food.

Tags

CCSS.7.SP.A.1

CCSS.HSS.IC.A.1

You want to know what is the most favorite sport of 10th graders at a high school. You ask 10th graders who want to participate to go to the office during their Lunch to complete a survey. This is...

• Biased, because no one likes sports.

• Unbiased

• Biased, because people were randomly selected

• Biased, because it is a volunteer sample, meaning only people who are interested will willingly go complete the survey. Also, people may not be willing to miss lunch for a survey.

Tags

CCSS.7.SP.A.1

CCSS.HSS.IC.A.1

An employer wants to know how their 500 employees like working for them. Which is the most representative sample?

• Ask the first 75 people to show up for work

• Randomly select the names of 10 employees

• Poll the Employees of the Month for the past year

• Randomly select the names of 75 employees

Tags

CCSS.7.SP.A.1

CCSS.HSS.IC.A.1

To find out what sort of events they should plan, the student government officers at Truth send a survey to 30 students whose names were randomly selected. The population they are interested in is...

• The 30 students who were sent the survey

• Only the students who respond to the survey

• All students at Truth

• All middle school students in DC

Tags

CCSS.7.SP.A.1

CCSS.HSS.IC.A.1

To find out what sort of events they should plan, the student government officers at Truth send a survey to 30 students whose names were randomly selected. The sample is...

• The 30 students who were sent the survey

• All students at Truth

• The student government officers

Tags

CCSS.7.SP.A.1

CCSS.HSS.IC.A.1