openintro (version 1.3)

textbooks: Textbook data for UCLA Bookstore and Amazon

Description

A random sample was taken of nearly 10% of UCLA courses. The most expensive textbook for each course was identified, and its new price at the UCLA Bookstore and on Amazon.com were recorded.

Usage

data(textbooks)

source

This data was collected by David M Diez on April 24th.

Details

The sample represents only courses where textbooks were listed online through UCLA Bookstore's website. The most expensive textbook was selected based on the UCLA Bookstore price, which may insert bias into the data; for this reason, it may be beneficial to analyze only the data where more is "N".

References

See Section 5.1 of the Open Intro Statistics textbook: http://www.openintro.org/

Examples

data(textbooks)
#===> an improper analysis <===#
boxPlot(textbooks$uclaNew, xlim=c(0.5,2.5))
boxPlot(textbooks$amazNew, add=2)
axis(1, at=1:2, labels=c('UCLA Bookstore', 'Amazon'))
t.test(textbooks$uclaNew, textbooks$amazNew)

#===> a reasonable analysis <===#
#     the differences are moderately skewed
#     the sample size is sufficiently large to justify t test
histPlot(textbooks$diff)
t.test(textbooks$diff)