To Notes

IT 223 -- 1/10/11

 

Review Problems

  1. What is the proper filename for project submissions?

    Ans: proj1-smithx.doc, where you replace Smith by your last name.

  2. What do the terms inner fence and outer fence mean?

    Ans: The two inner fences are located at Q1 - 1.5 x IQR and Q3 + 1.5 x IQR. The two outer fences are located at Q1 - 3.0 x IQR and Q3 + 3.0 x IQR. Extreme outliers are located to the outside of the outer fences. Mild or medium outliers are located between the inner and outer fences.

  3. Match the descriptions with the histograms below:

    1. The gender of all persons in a college class (male = 0, female = 1). Ans: iv.

    2. The handedness of all persons in a college class (left handed = 0, right handed = 1). Ans: iii.

    3. The heights of all married persons counted separately. Ans: i.

    4. The heights of all persons in families where both parents are 28 years old or less. Ans: ii

    5. The heights of all automobiles. Ans: v.

    6. The incomes of all persons in the U.S. Ans: vi.

  4. Draw the histogram in each case. Note: [a,b) denotes an interval that is closed on the left (includes a) and open on the right (does not include b).

    Caution: what does it mean for histograms (b) and (c) to have bins of different widths?

    (a)
    Bin Count
    [0,1) 1
    [1,2) 3
    [2,3) 4
    [3,4] 1
    		(b)
    Bin Count
    [0,1) 2
    [1,2) 4
    [2,4] 1
    		(c)
    Bin Count
    [0,1) 2
    [1,2) 4
    [2,2.5) 3
    [2.5,3] 1

  5. Compute the median for each histogram in the preceding problem by using interpolation in the bar that contains the median.

    Answers for Problems 5 and 6.

  6. Compute the interquartile range of the histogram of Problem 12c.

    Answers for Problem 7.

  7. Draw the histogram without bar lines of

    1. the incomes of all persons in the U. S.

      Ans: A skewed histogram with a peak at about 35 or 40 thousand, but with a long right tail that extends all the way past 1 billion.

    2. the GPAs of all students at DePaul.

      Ans: A bell-shaped histogram with peak around 3.0. There may be a secondary peak around 2.0, representing those students that have just come off of academic probation. The height of the histogram can only be nonzero in the range from 0 to 4.

    3. the number of years of schooling of all persons in the U. S.

      Ans: A bell-shaped peak around 12 years (most people finish highschool, less people attend college).

    4. the IQs of all persons in the U.S.

      Ans: A bell-shaped curve with center at 100 and spread 15.

  8. What do the initials SPSS mean?

    Ans: Statistical Package for the Social Sciences

  9. How do you accomplish the following in SPSS?

    1. Create a new dataset.

      Ans: Select New >> Data. Then type the data into the Data View.

    2. Change a variable name.

      Ans: Change the variable name in the Name columns of the Variable View.

    3. Add a label to a variable.

      Ans: Enter the label in the Label column in the Variable View.

    4. Import a dataset from an Excel file.

      Ans: Select Import >> Data. Set the filetype to .xls and open the desired Excel file. Then indicate the worksheet you want to use and whether the variable names are in the first row.

    5. Print a dataset.

      Ans: Select Analyze >> Reports >> Case Summaries. Select the variables that you want to print.

    6. Obtain Q0, Q1, Q2, Q3, and Q4 for a dataset.

      Ans: Select Analyze >> Descriptive Statistics >> Explore... Click the Statistics button and check the Percentiles button.

    7. Obtain a histogram and a boxplot.

      Ans: In addition to the answer 17f click the Plots button and select Histogram. The Stemplot is not needed.

 

Descriptive Statistics

 

Comparison of Mean and Median

 

Project 2