Descriptive Statistics

Lesson 14

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. 

Anchor Problems

?

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

Create a free account or sign in to access the Guiding Questions for this Anchor Problem.

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

Create a free account or sign in to access the Guiding Questions for this Anchor Problem.

Problem Set

?

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

Target Task

?

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