The predicted values show the fitted values of selected characteristics at the specified factor settings. The fitted values are based on the model that you specified.
If there are minimal interactions between the factors or if the interactions are correctly accounted for by the predictions, the observed results from the follow-up confirmation runs should be similar to the predicted results. On the other hand, if there is substantial disagreement between the predicted and the observed results, then there may be unaccounted for interactions or unforeseen noise effects. This suggests that more investigation is necessary.
Use the predicted values to determine which factor settings lead to the best result for your product or process.
The experimenters narrowed the choices to the second and fourth combinations. Both have Variety 2, Fertilizer 2, and Water 2. The only difference is in the level of Light. The experimenters ultimately chose the second combination because the standard deviation is substantially less for that combination and because lower light levels substantially reduce expenses.
You should perform confirmations runs at the selected levels to confirm that the predicted values are reliable. For the basil data, the selected levels were used in the original experiment, so the experimenters first verified the predictions against the observations from the original experiment. The original results agree quite closely with the predicted values, as shown in the table below.