The hardness of compressed tablets may be related to the pressure applied in the tablet press, and to the compression time. An experimenter carried out an experiment to investigate the effects of pressure, and time, on hardness. The results were analyzed by two-way analysis of variance with interaction. The ANOVA table is shown below (DF: degree of freedom). CA3-Fig 2

a. Test each null hypothesis, i.e. say whether you accept or reject it, giving a reason for your decision in each case. 

b. State your conclusions correctly and completely, but without using any statistical language, for the benefit of an inexpert audience who reads the report. 

c. How many different pressures were included in the experiment? How do you know? 

d. Sketch an interaction plot that could represent the information in the ANOVA table above. 

e. A different choice of factor levels for "Pressure" could have resulted in different experimental conclusion. Explain this statement suggested by an expert.