# 6th Grade - Selecting A Sample

 Grade Level: 6th Skill: Statistics Topic: Selecting a Sample Goal: Identify different ways of selecting a sample (e.g., convenience sampling, responses to a survey, random sampling) and which method makes a sample more representative for a population. Skill Description: Understand that a sample is a survey that is taken by only looking at part of a population. A sample should only be used when surveying the population will be timely or costly. There are different types of samples that can be taken. Identify each of the different sample types required for sixth grade: convenience, random, and systematic. Understand that a convenience survey consists a of a sample group that already exists. Conducting a survey to find the most popular music amongst 6th graders and using the students in your homeroom would be an example of a convenience survey. Often times, convenience samples don’t represent the entire population and can make the survey biased. A biased survey does not fairly represent the entire population and at its results are often misleading. A random sample, however is the most reliable sample and will be the least biased of all sample types. A random sample best represents the entire population because all members of the population have an equally likely chance to be included in the survey, however only a set about will be chosen. An example of a random sample is the names of all students in a school being placed in a bucket and 50 names being drawn to choose the sample group. . A systematic sample is another fairly reliable sampling method. When a pattern is used to find the sample group, a systematic sample is being conducted. For instance, if a list of students from a school is printed and every 10th student is interviewed, this is a systematic sample. This sampling method is not as representative of the entire population as a random sample, because each member of the population does not have an equally likely chance to be included, only the members that fit the pattern will be. Determine which sample method makes a specific sample more representative for a population.

## Building Blocks/Prerequisites

### Sample Problems

 (1) You need to find the most popular sport. Which sampling method would work best to help you? A) Ask your friends. B) Ask the basketball team. C) Ask random students off a list of all students. D) Ask the coach. (C) (2) Tatem needed to find the favorite ice cream of boys in her class. She asked the every other boy as they walked into homeroom. What kind of sample did Tatem take? (systematic) (3) Kelly wanted to find the favorite pop star of jr. high girls at her school. She walked around the cafeteria at lunch and asked each girl inside. What kind of sample did Kelly use? (convenience) (4) Jacob was given the assignment to find the most popular summer movie for jr. high kids in Encino, California. He stood outside a movie theatre in Encino for 3 hours and asked the jr. high kids that were going in. What kind of survey did he conduct? Was it representive for the entire population? (Since Jacob used a convenience sample, it was not representative of the entire population. Kids on the other side of town were left out.) (5) Gwen was asked to collect data to find the most popular video game amongst the students at her jr. high. The principal gave her a set of cards with the names and phone numbers for all students at the jr. high. Gwen placed the cards in a box and shook it up. She then drew out the cards one at a time, called the student and put the card back. She surveyed a total of 20 students out of the 432 in the box. What kind of sample did Gwen use? Would her survey likely be representative of the population? (random. Yes, each student had an opportunity to be chosen, even though she only chose 20.)

### Online Resources

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