Regression (Textbook Cost) (Optional), Linear Regression and Correlation | Statistics

Learning objectives

Regression (Textbook Cost)

Student Learning Outcomes

The student will calculate and construct the line of best fit between two variables.
The student will evaluate the relationship between two variables to determine whether that relationship is significant.

Collect the Data

Survey 10 textbooks. Collect bivariate data (number of pages in a textbook, the cost of the textbook).

Complete the table.

Number of Pages	Cost of Textbook

Which variable should be the dependent variable and which should be the independent variable? Why?
Graph pages vs. cost. Plot the points on the graph in Analyze the Data. Label both axes with words. Scale both axes.

Analyze the Data

Enter your data into a calculator or computer. Write the linear equation, rounding to four decimal places.

Calculate the following:
1. a = ______
2. b = ______
3. correlation = ______
4. n = ______
5. equation: y = ______
6. Is the correlation significant? Why or why not? (Answer in complete sentences.)
Supply an answer for the following scenarios:
1. For a textbook with 400 pages, predict the cost.
2. For a textbook with 600 pages, predict the cost.
Obtain the graph on a calculator or computer. Sketch the regression line.
View original figure (external; image not reproduced in this text edition)
Original figure description: Blank graph with vertical and horizontal axes.

Discussion Questions

Answer each question in complete sentences.
1. Does the line seem to fit the data? Why?
2. What does the correlation imply about the relationship between the number of pages and the cost?
Are there any outliers? If so, which point is an outlier?
Should the outlier, if it exists, be removed? Why or why not?

Attribution. Statistics, OpenStax, Rice University, and the contributing authors credited in the book. Licensed under Creative Commons Attribution 4.0 International. Source revision 7dea80ae28 of openstax/osbooks-statistics (2026-04-23). CC BY 4.0. Original source ↗. Text edition of a pinned CC BY 4.0 source revision of the OpenStax book, converted from CNXML by the EvidenceHelix importer. Original prose, learning objectives, tables, exercises, glossary and captions are preserved; images are not copied (figures link to the original source and keep their credits). No new content was added. Later revisions of this book can carry different licence terms and are not used.