Descriptive Statistics

Lesson 14

Math

Unit 2

9th Grade

Lesson 14 of 22

Objective


Describe relative and relative conditional frequencies of two-way tables.

Common Core Standards


Core Standards

  • HSS-ID.B.5 — Summarize categorical data for two categories in two-way frequency tables. Interpret relative frequencies in the context of the data (including joint, marginal, and conditional relative frequencies). Recognize possible associations and trends in the data.

Foundational Standards

  • 8.SP.A.4

Criteria for Success


  1. Describe that frequencies are measured not only in fixed amounts but also in relative percentages.
  2. Understand that when the percentage of one category is calculated in comparison to the total of another category or the total of the data set, this is a relative frequency. 
  3. Calculate the relative frequency by determining which category total the frequency is relative to. Calculate the relative frequency compared to the sample: "What percent of people surveyed own a red car?", the relative frequency compared to another variable: "What percentage of women own a red car?", or the relative frequency of two combined variables to the sample: "What percentage of the people surveyed are women who own red cars?" 
  4. Describe possible associations between variables in a two-way table. 

Tips for Teachers


This lesson starts to get at how a two-way table can show association between two variables using relative and joint frequencies. This work will continue in Geometry when students study probability. 

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Anchor Problems

25-30 minutes


Problem 1

100 students want to have burritos for lunch. 49 of those students are women. 75 students want tacos, and 26 students want quesadillas. 103 women were asked their lunch choices. 20 students who want quesadillas are men. 

Guiding Questions

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Problem 2

Using the table you created in Anchor Problem #1, describe: 

  • What percentage of people surveyed are women? 
  • What percentage of people surveyed are women who ordered quesadillas? 
  • What percentage of people surveyed ordered quesadillas? 
  • What percentage of women surveyed ordered quesadillas? 

Guiding Questions

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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


Juniors and seniors were asked if they plan to attend college immediately after graduation, seek full-time employment, or choose some other option. A random sample of 100 students was selected from those who completed the survey. 

Below is a chart of some of the relative frequencies. Complete the calculations for each of the blank cells. 

A school website article indicated that “a vast majority of students from our school plan to attend college.” Do you agree or disagree with that article? Explain why you agree or disagree.

References

EngageNY Mathematics Algebra I > Module 2 > Topic C > Lesson 10Exit Ticket

Algebra I > Module 2 > Topic C > Lesson 10 of the New York State Common Core Mathematics Curriculum from EngageNY and Great Minds. © 2015 Great Minds. Licensed by EngageNY of the New York State Education Department under the CC BY-NC-SA 3.0 US license. Accessed Dec. 2, 2016, 5:15 p.m..

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.

Next

Create scatterplots and identify function shapes in scatterplots.

Lesson 15
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Lesson Map

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

Topic A: Descriptive Statistics in Univariate Data

Topic B: Descriptive Statistics in Bivariate Data

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