Factorial design effects of plant density, pattern and light availability on the caffeine, chlorogenic acids, lipids, reducing sugars and ash contents of Coffea arabica L. beans and leaves
Factorial design experiments were executed to determine the effects of plant pattern and density as well as the degree of light availability on the caffeine, chlorogenic acids, lipids, reducing sugars and ash contents of beans and leaves of Coffea arabica samples. Samples exposed to direct sunlight have smaller caffeine contents (0.68 μg mL−1) than those partially protected from sun exposure (0.99 μg mL−1). High plant density samples have higher caffeine contents (0.98 μg mL−1) than those from lower density plots (0.69 μg mL−1). Square plant pattern samples, probably less exposed to the sun, have higher caffeine contents (0.97 μg mL−1) than those from rectangular plant patterns (0.70 μg mL−1). Paired t-tests applied to factorial design experiments block out extraneous variance sources and permit the determination of effects with greater precision than simply comparing the means of two different groups of data.