13 . 3 . An article in Industrial Quality Control ( 1956 , PP . 5 - 8 ) describes an experiment to investigate the effect of glass type and phosphor type on the bright ness of a television tube . The response measured is the current necessary ( in microamps ) to obtain a specified brightness level . The data are shown in Table 13 E . 1 . Analyze the data and draw conclu - sions . ABLE ISE . Data for Exercise 13.1 Phosphor Type Glass Type 80 300 290 290 310 205 285 295 290 230 260 10 220 235 240 225 240 235 230