An importer of decorative ceramic tile samples 50 tiles each day from incoming shipments. Some tiles are cracked or broken before or during transit, rendering them useless scrap. Sampling from incoming shipments for 30 days reveals that a total of 250 tiles are cracked or broken. The centreline on the p chart for these data is
A) 0.250.
B) 1.83.
C) 2.5.
D) 0.167.
E) 6.1.

Question

Quizplus · Accepted Answer

The centerline of a p-chart is calculated as the average proportion of defective items. Here, 250 tiles are defective out of 1500 sampled (50 tiles/day * 30 days), so the centerline is 250/1500 = 0.167.

An Importer of Decorative Ceramic Tile Samples 50 Tiles Each