Project 23
Project description

Suppose we would like to explore the question: Does it rain more in Tacoma, Washington or Seattle, Washington?

  1. Fit and interpret a simple linear regression model of annual precipitation in Tacoma modeled on annual precipitation in Seattle to address this question. Explain why such an approach is reasonable, and to what extent it answers the question.
  2. Do the same to address the question of whether it rains more in Tacoma, Washington or Portland, Oregon.
  3. You may ignore the fact that this data set is a time series and pretend for the present that it is a simple random sample of years, with all years being independent of each other. We will explore the extent to which this is not true and some of the modeling ramifications of this in Project 28.

Background on the data set

This data set gives annual precipitation totals for Portland (OR), Tacoma (WA), and Seattle (WA) for the years 1966-2006, precipitation being defined as: "Any form of water particles-liquid or solid-that falls from the atmosphere and reaches the ground."

Data Source: Western Regional Climate Center (, specifically "Monthly Totals" under "Monthly Precipitation Listings" for the following: Portland, Tacoma, and Seattle. The definition of precipitation quoted above is also from this website, specifically in their climate and weather terms glossary. (All links accessed June 14, 2008.)

Variables in the data set
The variables in the data set are as follows:
year(years)year of precipitation measurement
cityPortland, Seattle, or Tacomalocation of measurement
precipitationinchesamount of annual precipiation
Link to the data set
The full data set in csv format is at: