Statistics

Lesson 2

Math

Unit 7

7th Grade

Lesson 2 of 9

Objective


Describe sampling methods that result in representative samples.

Common Core Standards


Core Standards

  • 7.SP.A.1 — Understand that statistics can be used to gain information about a population by examining a sample of the population; generalizations about a population from a sample are valid only if the sample is representative of that population. Understand that random sampling tends to produce representative samples and support valid inferences.

Foundational Standards

  • 6.SP.A.1
  • 6.SP.B.5

Criteria for Success


  1. Understand that some sampling methods can lead to biased or unrepresentative samples that do not represent the population.
  2. Understand that a random sample, in which every entry in the population has an equal chance of being part of the sample, tends to be representative of the population.
  3. Identify and describe sampling methods that will result in samples representative of the population.

Tips for Teachers


In Lessons 2 and 3, students define and experiment with random sampling. In Lesson 2, students discover that there are several different ways to collect sample data of a population, but not all of these methods are representative or fair. Students begin to understand that a random sample tends to lead to an unbiased sample of the population. In Lesson 3, students will engage in an activity where they can see how random sampling leads to more accurate information about a population.

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Anchor Problems

25-30 minutes


Problem 1

In a poll of Mr. Briggs’s math class, 67% of the students say that math is their favorite academic subject. The editor of the school paper is in the class, and he wants to write an article for the paper saying that math is the most popular subject at the school. 

Explain why this is not a valid conclusion and suggest a way to gather better data to determine what subject is most popular.

Guiding Questions

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Student Response

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References

Illustrative Mathematics Mr. Brigg's Class Likes Math

Mr. Brigg's Class Likes Math, accessed on March 29, 2018, 12:35 p.m., is licensed by Illustrative Mathematics under either the CC BY 4.0 or CC BY-NC-SA 4.0. For further information, contact Illustrative Mathematics.

Problem 2

Tonya wants to determine the average number of books that students in her school read each month. She decides that she will collect a sample of responses from 25 students in her school. Below are some methods she is considering using to collect her data. Discuss pros and cons for using each method to collect sample data and which method, either on this list or a new idea, that you think Tonya should use.

a.   Ask the students in her eighth-grade homeroom

b.   Ask the students in her sister’s sixth-grade math class

c.   Ask the students in the after-school book club

d.   Ask the first 25 students she sees on a Monday morning

e.   Assign each student in the school a number, randomly choose 25 numbers, and ask those students

Guiding Questions

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Student Response

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Problem Set

15-20 minutes


Give your students more opportunities to practice the skills in this lesson with a downloadable problem set aligned to the daily objective.

Target Task

5-10 minutes


A teacher wants to treat his homeroom class for having perfect attendance the last three months. He is deciding between offering a pancake breakfast in the morning or a pizza lunch in the afternoon. 

To help him decide, he takes a poll of the first 10 students to arrive at school in the morning. 

Do you agree with the teacher’s choice of sampling method? Explain why you think this method will be representative of the class, or describe a different method the teacher should use to get a representative sample. 

Student Response

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Additional Practice


The following resources include problems and activities aligned to the objective of the lesson that can be used for additional practice or to create your own problem set.

  • Challenge: One common way to collect data is to send surveys to a random group of people in the mail. The data that is collected is from those who choose to send the survey back. Do you think this way of collecting data is representative or biased? Explain your reasoning. 

Next

Generate a random sample for a statistical question.

Lesson 3
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Lesson Map

A7CB09C2-D12F-4F55-80DB-37298FF0A765

Topic A: Understanding Populations and Samples

Topic B: Using Sample Data to Draw Inferences About a Population

Topic C: Using Sample Data to Compare Two or More Populations

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