7/21/2019 Binh Nguyen - Excel Write Up

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6. The Conclusions

In term of appearance by visual inspection, the data points fit with 1storder kinetics better

than 2ndorder. Looking at the superimposed line, one could easily see that most of the data point

fall into the line, with the exception of 1 or maybe 2 points, which appear to be random or

experimental errors. For the fit line of 2

nd

order model, even though the data points are not toofar off the line, most of them are not on the line either. It is not totally obvious, but if the first

two points are excluded, one could easily argue that the data points could fit in a curve (see the

pencil line on the graph. Therefore, the data points on 2ndorder model appear to be systematic

long-term trend.

In term of R2values, 1storder model also seems to be a better fit. Conceptually, the R2

coefficient of determination is a statistical measure of how well the regression line approximates

the real data points (definition taken from Wikipedia). R2 takes values from 0 to 1, in which the

closer to 1, the better fit. In this case, the 1storder model has R2value of 0.9959 and the 2ndorder

model has R2value of 0.9742. It is worth noting that an R2value of 0.9742 is not a bad value,

statistically. However, we can argue that 1st

order model has a better fitting.

In term of errors, the 1storder model also has smaller errors compared to the 2ndorder

model. The absolute errors of the 2ndorder model are about 10 times bigger than those of the 1st

order model. The relative errors of both models, in percentage, are calculated in the table below:

1st order 2nd order

slope -2.14 5.42

intercept -1.39 3.06

One could easily see that the relative errors of 2ndorder model are bigger than those of 1stmodel.

In conclusion, 1storder model is a better fit for the given data. It has better visual fitting,

better R2value and smaller errors in slope and intercept.

7. This report uses information from the lab handout written by WEH and revised by WEH and

TAF. The definition of R2value was adapted from Wikipedia.