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  1. In newspapers or magazines, try to find examples of plots of data like the ones in this chapter. You will probably not be successful because graphs depicting the spread of data are unfortunately very rare in the media. Try to find any graph that does depict spread in some way.

  2. In the library, look for box plots and plots of means with spread in scientific journals.

  3. box plot from Statistical Knowledge Quiz about pulse rates From the Statistical Knowledge Quiz: In this boxplot of resting pulse rates from a group of university students, the interquartile range is about 15 and the median is about 72. True or False?

    The distribution of pulse rates is very skewed. True or False?

  4. If you are using a statistical computer package with Seeing Statistics, select some variables from the sample files that came with the program. Construct box plots and plots of mean with spread (possibly by hand) of some continuous or quantitative variables that interest you. Write a brief description of the variable based on the plots, being sure to indicate whether the data are roughly symmetric or skewed. Here are some suggestions:

    • JMP
      Obliquity in cassini.jmp
      defects in braces.jmp
      age in carpoll.jmp

    • Minitab
      Control in cholest.mtw
      oxygen in oxygen.mtw

    • StatView
      MedianValue and NOX in BostonHousingData
      calories in CandyBars

  5. A sample of students entering a major university completed a long survey asking about their attitudes, high school activities, their academic plans, etc. Students also reported their SAT Verbal and Math scores. Subsequently it was possible to obtain the true scores received by these students as reported by the Educational Testing Service. The following variables are available in the downloadable dataset for 170 students:

    • Sex: 1 = Male, 2 = Female
    • SATV: SAT-Verbal score as reported by the student on the survey
    • SATM: SAT-Math score as reported by the student on the survey
    • TRUESATV: SAT-Verbal score as reported to the university by ETS
    • TRUESATM: SAT-Math score as reported to the university by ETS

    Construct boxplots and mean with spread plots for each of these variables. Compare the boxplot of SATV to TRUESATV to see if it appears that students answered truthfully about their scores. Do the same for SATM and TRUESATM.

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© 1999, Duxbury Press.