1/16/2013

Types of Variables

• A quantitative variable is a variable that takes on numerical values for which arithmetic makes sense.
• A categorical or qualitative variable is a variable that records which category a person place or thing falls into.

Questions about data

• What variables are being measured?
• Are these variables appropriate for answering the question(s) of interest?
• What are the units of measurement?
• How are the data recorded?

Graphical Displays

• Why are graphing techniques useful?
  • Examine the overall shape of a distribution - (symmetric or skewed?)
  • Look for deviations from the overall shape - (unusual observations, gaps, etc.)
  • Locate the center of the distribution

Stem and Leaf Plots

• Separate each observation into a stem and a leaf.
• List the stems vertically in increasing order from top to bottom.
• Add the leaves (typically the last digit) to the right of the stems.

Histograms

• Divide the range of the data into classes of equal width.
• Count the number of observations in each class.
• Compute the relative frequency or percent for each class.
• Erect bars over each class interval.

Graphical Displays with Minitab (Open p:\data\math\hartlaub\SportsStats\Day1 F2013.mtw)

• Bar Charts (Graph > Bar Chart)
• Pie Charts (Graph > Pie Chart)
• Dotplots (Graph > Dotplot)
• Stemplots (Graph > Stem-and-Leaf)
• Histograms (Graph > Histogram)

Comments and Questions on Chapter 1 Reading

Introduction to Simulation

• Introduction to the Practice of Statistics web site
• SRIS web site
• Minitab
• Statkey

Class exercises - Getting comfortable with Minitab

• Compare (graphically and numerically) the reaction times of women and men.
• Compare (graphically and numerically) the reaction times of different classes.
• Compare (graphically and numerically) the reaction times of varsity athletes with those students who are not varsity athletes.
• Replicate the simulation methods used in the examples for Chapter 1. Are your results exactly the same? Are your conclusions the same?

Reading Assignment - Please read Chapter 2 for class on Friday.