S3N03 - Assignment #1

Statistics 3N03/3J04 - Assignment #1

2004-09-26

Due: 2004-10-04 18:00

Do your graphs and calculations in R. Submit your work as a report, pasting the graphs into a word processor and adding comments and discussion. The first question is from Montgomery & Runger, Applied Statistics and Probability for Engineers, 3rd edition, and some data sets are available on the accompanying CD.

Question 1: 14-4 (p 519)

Do graphical analyses using comparative box plots to compare baked density between the firing temperatures and between the furnace positions. Give "interaction plots" like the one in Figure 14-8 (p 516): plot the mean baked density against firing temperature, separately for each furnace position, and plot the mean baked density against furnace position, separately for each firing temperature. Repeat the graphs with baked density on a log scale. State your conclusions. (The question asks for a two-factor analysis of variance but you will do that in Assignment #3.)

Hints: Enter the data as three columns in a data frame, putting the baked density in the first column, a code for firing temperature in the second, and a code for furnace position in the third. To plot on a log scale, you can add the option log="y" to the plot or boxplot command to transform the Y-axis, or you can compute a new column of log-transformed baked densities.

Question 2: Glass fragments

Get the data frame fgl from the MASS library in R. To do this, attach the library with library(MASS) then copy the data frame to your workspace with data(fgl). To see the data documentation, enter ?fgl.

Using boxplots and scatterplot matrices, explore the data. If you had a new fragment of glass and knew that it was either headlamp glass, vehicle window glass or window float glass, which variables would you use to decide which type it was?

Question 3: Two artificially generated time series

The file tss.html gives two time series. Explore each with a time series plot, a lag 1 plot, a lag 2 plot, a box plot, and a histogram. Put both box plots on the same graph. Compute the mean and variance of each series. In what ways are the series the same? How are they different?