nary (e.g. pass/fail) or from a discrete list of options. Lyu et al.5
the region of interest. Arendts et al.9 developed a method for evaluating gage R&R for attri-
bute data collected from inspection tasks such as inclusions in micrographs of steel or individual pixels of a monitor. Specifically, their method takes into special consideration the distribution of the defects within the inspection field. Burke studied errors associated with industrial inspec- tion tasks, but only considered variable measurements and binary decision inspection tasks.6
Das7 conducted a case
study on the measurement error associated with a subjec- tive length decision.
The medical field also has needs for subjective evaluation of images; these are not immune to measurement error.6-7 al.8
Lee et investigated the subjective evaluation of X-ray CT head
images by radiologists. This work showed that the agree- ment among six readers was statistically significant, but there were large variations among readers as well as within a reader. This method did not include the variation of size of
investigated misinter-
pretation rate of CT scans of hospital emergency department staff. None of these, however, provides a method for deter- mining measurement error when the inspection output is the size, shape, and location of a region.
The most relevant work in the metalcasting field is that by Schorn 10-11
who reported the difficulty in achieving consis-
tency in the inspection of aluminum automotive wheel cast- ings. His approach also did not take into account the size or the shape of the defective region.
While there are many sources available on measurement error, the review of literature reveals very little regarding inspection tasks pertinent to this specific situation (when there could be several types of anomalies, and the measure- ment output is their shape, size and location.) Because of this need, the methodology presented in the next sections was developed.
Figure 1. Photographs of some representative comparator plates from the SCRATA Comparator Plate set. 2 Type XII Surface Roughness Acceptable Non-Acceptable
Figure 2. Representative photographs that are included in the MSS SP-55 standard. 3
8 International Journal of Metalcasting/Summer 2011
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