Today, I used R to evaluate the variation in sugar cane weight caused by different pests. The goal was to understand the fundamentals of ANOVA (Analysis of Variation ) and how to interpret the results.
The boxplot was the best option to graphically represent the data. The difference in mean between the control and the remaining samples strongly suggests that the pests had a significant effect on the yeild. An ANOVA on these results found a significant variation among conditions, F ratio > 1, P-value < 0.05.
|Analysis of Variation Results|
At a confidence coefficient of 0.95, or 95%, a post hoc Tukey test showed that the sugar yield did not change significantly depending on the type of pests. The Tukey test supported observations from the boxplot, showing that only the control group was significantly different from the remaining groups. In simpler terms, I cannot be 95% sure there is a difference in yeild between various types of pests.
|Tukey Test Results|
The coding is as follows:
The link for the dataset is attached: http://bit.ly/1LELKm1
P. C. Mahalanobis and S. S. Bose, “A Statistical Note on the Effect of Pests on the Yield of Sugarcane and the Quality of Cane-Juice,” The Indian Journal of Statistics, vol. 1, no. 4, pp. 399–406, 1934.