Biased or Unbiased Sampling

If I wanted to know how many blades of grass are inside the track, which sampling method could I use?

• Have my students count every blade of grass

• Guess

• Divide the grassy area into 1 inch sections, randomly pick several sections to count, average them together and multiply that by the total square inches.

At a middle school, the 7th graders will conduct a survey to decide where they want to go on a field trip. Which method will result in the least biased decision?

• to randomly ask 8th grade students who went on a field trip last year

• to randomly choose some 7th grade students to select a location

• to ask all 7th grade teachers and administrators for a location

• to ask the student council to choose a location

Unbiased sampling is:

• when you choose the group you think will give you the answer you want, accept volunteers or survey by convenience

• when any member of the population is equally likely to be chosen for the sample

To determine the most popular children’s programs, a television station asks parents to call in and complete a phone survey.

• Biased Sample

• Unbiased Sample

To determine how often people eat out, every tenth person entering a Chinese restaurant is surveyed.

• Biased Sample

• Unbiased Sample

A high school is going to have a party for their graduating seniors. They want to serve food that most of the seniors like. They pick 25 random names from a hat and survey those students. Is this a biased sample or unbiased sample?

• Biased Sample

• Unbiased Sample

Green Valley Middle School conducted a survey of 125 random students asking them how much time they spend each night on homework. Is this a biased sample or unbiased sample?

• Biased Sample

• Unbiased Sample

Debbie surveyed all the students who ride the bus to school to find how long they take to get ready in the morning. Is this a biased sample or unbiased sample?

• Biased Sample

• Unbiased Sample

What type of sampling methods would be the most likely to produce INVALID survey results?

• Unbiased or fair sampling

• Biased or unfair sampling

• Unbiased or unfair sampling

• Biased or fair sampling

When a sample does not accurately represent the population it is a:

• Unbiased sample

• Biased sample