Tatoo Problem (See Pages 31-32 in Intro Stats)

Tattoos (source: Intro Stats by De Veax & Velleman 2004). A study by the University of Texas Southwestern Medical Center examined 626 people to see if there was an increased risk of contracting hepatitis C associated with having a tattoo. If a subject had a tattoo, researchers asked whether it had been done in a commercial tattoo parlor or elsewhere.

The worksheet looks like the following.

We want the table in the session window to look similar to the table on page 32. Highlight the first two columns (C1-T and C2-T) of your worksheet. Click on EDITOR> Set Column> Value order and then check Order of occurrence in worksheet. Click OK. We next want the counts, row percentages, column percentages, and total percentages. Select Stat>Tables>Cross Tabulation and Chi-Square. Fill in the dialog boxes and options as shown below. Click OK. The output in the session window looks like the following.

Tabulated statistics: Hepatitis, Tattoo

Using frequencies in count

Rows: Hepatitis Columns: Tattoo

parlor else no All yes 17 8 18 43 39.53 18.60 41.86 100.00 32.69 13.11 3.51 6.87 2.716 1.278 2.875 6.869 no 35 53 495 583 6.00 9.09 84.91 100.00 67.31 86.89 96.49 93.13 5.591 8.466 79.073 93.131

All 52 61 513 626 8.31 9.74 81.95 100.00 100.00 100.00 100.00 100.00 8.307 9.744 81.949 100.000

Cell Contents: Count % of Row % of Column % of Total

 Who? What individuals do the data describe?  How? How many individuals appear in the data set and how was the data collected?  What? How many variables do the data contain? Categorical or quantitative?  Why? What purpose do the data have? Where was the data collected?

1. What percent of the subjects have Hepatitis C? 2. What percent of the subjects did not have a tattoo? 3. What percent of the subjects that had a tattoo done in a commercial parlor have Hepatitis C? 4. What percent of the subjects that had a tattoo done elsewhere have Hepatitis C? 5. What percent of the subjects that had no tattoo have Hepatitis C? 6. What percent of the subjects that have Hepatitis C had no tattoo?

To produce a segmented bar chart click on Graph> Bar Chart and fill in the dialog boxes as shown below. Click on Bar Chart Options and fill check the options as shown below. Clicking OK produces the segmented bar chart.

Chart of count vs Tattoo, Hepatitis

100 Hepatitis y es no

80 t n u o c

60 f o

t n e c

r 40 e P

0 Tattoo parlor else no Percent within levels of Tattoo.

Conclusion: