Population Sample Bias

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

• Unbiased sample

• Biased sample

Mrs. Croix is conducting a survey to find out the favorite snack of fifth and sixth graders. She will ask a sample of 100 students. Which of the groups below should be surveyed to get the BEST representative sample?

• 20 students from each of the 5 local fifth- and sixth-grade schools.

• The first 100 students who go to a local baseball game

Larger random sample sizes are more representative of a population.

• True

• False

Which random sample is the more likely it is to represent the population of a Jupiter Middle School  accurately?

• Five students of a school.

• Five hundred students of a school.

Tanya wants to know the percent of people likely to attend the upcoming musical at school. She asks each person in the musical how many people they know who are coming to make a prediction. Why is this sample biased?

• Drama students are more likely to lie.

• Musicals are better attended than plays.

• The drama teacher was not asked.

• The sample is not random and not representative of the entire school population.

Answer explanation

The sample is not random and not representative of the entire school population, as it only includes people involved in the musical, leading to bias.

In a certain school, students can choose whether to eat in the school’s cafeteria. A reporter working for the school’s newspaper polled students on their reactions to changes in the menu at the cafeteria. For each student leaving the cafeteria in one 20-minute time period, the reporter used a die to determine whether to stop the student and ask how he or she felt about the new menu. In the reporter’s article it was stated that a random sample of the students showed that 23% of the school’s student population was happy with the new menu. Which of the following statements is true?

• Because each student leaving the cafeteria was randomly selected and could choose to answer or not, this is a random sample of the student population, and the 23% is an accurate measurement of the school population’s view of the new menu.

• Because students self-selected whether to eat in the cafeteria, the sampling method might be biased and the sample might not be representative of all students in the school.

• The survey would have been more effective if the reporter had collected the data in one 10-minute time period rather than in one 20-minute time period.

• The survey would have been more effective if students who cared about the food could have called the reporter to tell how they felt about the new menu, so that only students with opinions on the subject would have been surveyed.

• Because no treatment was imposed on the students eating in the cafeteria, one cannot make any conclusions about the new menu.

A sample should be

• representative of  only middle school students only

• a very large group

• representative of the population

• representative of people who volunteer

At a middle school, the 7th graders will conduct a survey for where 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

You want to know what is the most favorite sport of 7th graders at BMS.  You ask 7th graders who want to participate to go to the office 5th period to complete a survey.  This is...

• Biased, because it is a convenience sample

• Unbiased

• Biased because it is an interval sample

• Biased because it is a volunteer sample

_______ is the entire group of objects or individuals considered for a survey.

• Sample

• Population

• Random Sample

• Quartile