50. The article Towards Improving the Properties of Plaster Moulds and Castings (J. Engrg. Manuf., x2##  4029.10, and x3##  3960.02 xi## x1##  4010.88, Carbon Sand Fiber Addition Addition Casting Wet-Mold

(%) (%) Hardness Strength 0 0 61.0 34.0 0 0 63.0 16.0 15 0 67.0 36.0 15 0 69.0 19.0 30 0 65.0 28.0 30 0 74.0 17.0 0 .25 69.0 49.0 0 .25 69.0 48.0 15 .25 69.0 43.0 15 .25 74.0 29.0 30 .25 74.0 31.0 30 .25 72.0 24.0 0 .50 67.0 55.0 0 .50 69.0 60.0 15 .50 69.0 45.0 15 .50 74.0 43.0 30 .50 74.0 22.0 30 .50 74.0 1991: 265—269) describes several ANOVAs carried out to study how the amount of carbon ber and sand additions affect various characteristics of the molding process. Here we give data on casting hardness and on wet-mold strength.

a. An ANOVA for wet-mold strength gives SSSand  705, SSFiber  1278, SSE  843, and SST  3105. Test for the presence of any effects using a  .05.

b. Carry out an ANOVA on the casting hardness observations using a  .05.

c. Make an interaction plot with sand percentage on the horizontal axis, and discuss the results of part

(b) in terms of what the plot shows.