As you learned at the beginning of this chapter, D. Seo et al. evaluated the marginal and internal gaps in Cerec3 partial ceramic crowns (PCC), using three different preparation designs: conventional functional cusp capping/shoulder margin (CFC), horizontal reduction of cusps (HRC), and complete reduction of cusps/shoulder margin (CRC). Sixty human first and second molars, without any caries or anatomical defects and of relatively comparable size, were randomly assigned to the three preparation designs. After fixation of PCCs to the 60 teeth, microcomputed tomography (μCT) scanning was performed to evaluate the marginal and internal gaps in the crowns.
The average internal gap (AIG) is the ratio of the total volume of the internal gap to the contact surface area. The table on page 525 presents summary statistics for the AIGs, in micrometers (μm).
a. Assuming that AIG is normally distributed for each preparation design, can we reasonably presume that the conditions for performing a one-way ANOVA are met?
b. Perform a one-way ANOVA to decide, at the 5% significance level, whether the data provide sufficient evidence to conclude that a difference exists in AIG means among the three preparation designs. Interpret your result.

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