We want to increase the yield of good transdermal patches (% of patches of acceptable quality in each batch) produced on the system that coats drug solution onto the backing film, dries it in a heat tunnel, attaches protective release liner film, then cuts the patches to size and places them into pouches.

Currently, too many patches come out with various defects.

Variables that we think may affect the yield of good patches are:

• Speed of the coating machine High / Low
• Temperature in the patch drying tunnel High / Low
• Air flow in the patch drying tunnel High / Low
• Viscosity of the coating solution High / Low
• Type of the coating nozzle Nozzle1/Nozzle2
• Filtering of the drug solution Filtered/Not filtered
• Width of the coating on the patch High / Low

The questions we need to answer are:

• Which variables affect the yield most?
• How big an effect do they have?

We only have time and ingredients to make 12 batches of transdermal patches.

How can we evaluate the effects of these 7 variables on the yield of good patches considering these constraints? Using Minitab, develop the design of experiments to be conducted.

After you have the DOE table, make up some numbers for the product yield in each of the experiments in that table, and then analyze those results (try to answer the questions listed above). Propose which of the factors you would like to study in future experiments to further improve process design.

Hint: when you create the "experimental" results for the product yield, it's better to do it manually rather than to use a random numbers generator. If you think that, for example, high temperature in the drying tunnel reduces the product yield, put some lower than average numbers in the yield column for the runs where that temperature is at the high level and higher yield numbers for the runs where that temperature is at the low level. In that case, you are more likely to find a statistically significant effect of that factor when you analyze the "experimental" results.