Yield  Time  Temp

50.95  76.0  170
47.35  80.5  165
50.99  78.0  182
44.96  89.0  185
41.89  93.0  180
41.44  92.1  172
51.79  77.8  170
50.78  84.0  180
42.48  87.3  165
49.80  75.0  172
48.74  85.0  185
46.20  90.0  176
50.49  85.0  178
52.78  79.2  174
49.71  83.0  168
52.75  82.0  179
39.41  94.0  181
43.63  91.4  184
38.19  95.0  173
50.92  81.1  169
46.55  88.8  183
44.28  91.0  178
48.72  87.0  175
49.13  86.0  175

The investigation concerns the influence of reaction time and temperature on process yield.
A description of this data that I read indicates that a nonlinear relationship is to be
expected.