Exploring data: Graphs and numerical summaries
Exploring data: Graphs and numerical summaries

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Exploring data: Graphs and numerical summaries

2.7 Surgical removal of tattoos

The final data set in this section is different from the others in that the data are not numerical. So far you have only seen numerical data in the form of measurements or counts. However, there is no reason why data should not be verbal or textual. Table 7 contains clinical data from 55 patients who have had forearm tattoos removed. Two different surgical methods were used; these are denoted by A and B in the table. The tattoos were of large, medium or small size, either deep or at moderate depth. The final result is scored from 1 to 4, where 1 represents a poor removal and 4 represents an excellent result. The gender of the patient is also shown.

Table 7 Surgical removal of tattoos

MethodGenderSizeDepthScore  MethodGenderSizeDepthScore
AMLargedeep1BMmediummoderate2
AMLargemoderate1BMlargemoderate1
BFSmalldeep1AMmediumdeep2
BMSmallmoderate4BMlargedeep3
BFLargedeep3AFlargemoderate1
BMMediummoderate4BFmediumdeep2
BMMediumdeep4AFmediumdeep1
AMLargedeep1AMmediummoderate3
AMLargemoderate4BMlargemoderate3
AMSmallmoderate4AMmediumdeep1
AMLargedeep1AFsmalldeep2
AMLargemoderate4AMlargemoderate2
AFSmallmoderate3BMlargedeep2
BMLargedeep3BMmediummoderate4
BMLargedeep2BMmediumdeep1
BFMediummoderate2BFmediummoderate3
BMLargedeep1BMlargemoderate2
BFMediumdeep1BMlargemoderate2
BFSmallmoderate3BMlargemoderate4
AFSmallmoderate4BMsmalldeep4
BMLargedeep2BMlargemoderate3
AMMediummoderate4BMlargedeep2
BMLargedeep4BMlargedeep3
BMLargemoderate4AMlargemoderate4
AMLargedeep4AMlargedeep2
BMMediummoderate3BMmediumdeep1
AMLargedeep1AMsmalldeep2
BMLargemoderate4

(Lunn, A.D. and McNeil, D.R. (1988) The SPIDA manual. Statistical Computing Laboratory, Sydney.)

What are the relative merits of the two methods of tattoo removal? Is one method simply better, or does the quality of the result depend upon the size or depth of the tattoo?

M248_1

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