Random Limited Biased

When you can not (or do not want) to count/survey everyone/thing in the population you use a SAMPLE.

Which best describes a sample?

• A sample is a complete count of every individual in the population.

• A sample is a subset of individuals chosen from a larger set.

If the population is ALL 7th Graders Then you want to take a sample from ALL 7th graders. A sample is part of the population but not all of it. Select the one below that is true

• A sample is a smaller group selected from the population

• A sample is the entire population

• A sample is a larger group than the population

• A representative sample is not related to the population

BEWARE: Your sample does not allow for someone in China to be represented.

If you survey students in your town then your population is limited to students in your town.

What makes a sample representative?

• The sample is representative if it includes people from all over the world

• The sample is representative if it includes people from the same town

• The sample is representative if it includes people from the same country

• The sample is representative if it accurately reflects the group it is supposed to represent

When taking a sample You want to choose individuals/objects FROM THE POPULATION Anyone in the population could potentially be part of the sample is ideal. Which below is the best way to take a sample?

• Only select individuals who are easily accessible

• Select individuals based on personal bias

• Select individuals randomly from the entire population

• Only select individuals who respond to a public survey

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.

For a survey, a company manager assigned a number to each of the company's 500 employees, and put the numbers in a bag. The manager chose 20 numbers and surveyed the employees with those numbers.

• biased

• random

Ms. Madson wants to know how many students will attend the next 7^th grade after school dance.  She places all the 7^th grade students’ names in a jar and selects 50. Is this random or biased sampling?

• Random

• Biased

You want to know how many students catch the bus to go home.  You go to the bus stop and ask students how they go home from school.  Is this a random sample or biased sample?

• BIASED

• RANDOM

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.

The sample represents the population.

Choose the answer that says "Representative Sample"

• Random Sample

• Biased Sample

• Representative Sample