8.SP.4: Analyzing Bivariate Categorical Data with Two-Way Tables: Understanding Patterns of Association

Grade: 8th Grade

Domain: SP: Statistics and Probability

Standard Description

Understand that patterns of association can also be seen in bivariate categorical data by displaying frequencies and relative frequencies in a two-way table. Construct and interpret a two-way table summarizing data on two categorical variables collected from the same subjects. Use relative frequencies calculated for rows or columns to describe possible association between the two variables. For example, collect data from students in your class on whether or not they have a curfew on school nights and whether or not they have assigned chores at home. Is there evidence that those who have a curfew also tend to have chores?

Domain Description

Analyse scatter plots for bivariate data to find connections between two quantities; find patterns such as outliers, clusters, linear and nonlinear association. Develop a basic understanding that straight lines can indicate a relationship between two quantitative variables. Look at scatter plots; if there's a suggestion of a linear relationship, draw a straight line to approximate the relationship and inspect the fit of the model by seeing how close the data points are to the line.

Use a linear model equation to address problems related to bivariate data, and understand what the slope and intercept signify. As an example, in a biological experiment, a slope of 1.5 cm/hr could mean that every extra hour of sunlight increases the mature plant height by 1.5 cm.

Comprehend that associations can be found in bivariate categorical data by visualizing frequencies in a two-way table. Make and interpret a two-way table that summarises data collected on two categorical variables from the same subjects. Use relative frequencies from rows or columns to indicate potential relationships between variables. As an example, collect data on the presence of a curfew and assigned chores among your classmates to explore possible linkages.