Resumen
- Efficient data collection (i.e. experimental design) is an important skill, but there is typically little opportunity to get experience. Textbooks introduce standard general-purpose designs, and then proceed with the analysis of data already collected. Here we explore another approach: for greenhouse experimentation, a software environment (JAVA applet) was developed that mimics a real situation of interest, namely optimising some fertilizer treatment in the presence of radiation and tempera-ture gradients. The greenhouse applet requires the user to set up an experiment with tomato plants in a greenhouse. To succeed, the user has to deal with the problem of selecting appropriate levels for a treatment variable, and with the many problems caused by diversity in raw material and experimental circumstances. The purpose of the experiment is to find the optimal dose of a new fertilizer. At the start, a set of 144 young tomato plants is available (12 trays of 3x4 plants). The young plants are all varying in initial weight. The user has to select some (or all) of the plants for the experiment and place them on the greenhouse tablet in the middle. The tablet is bordered on the left and the right with central heating devices (the thick black vertical lines). The tablet is also lighted by four high pressure sodium lamps. Consequently the positions on the tablet are not identical, and the differences in light and heat can be expected to have an effect on the growth. The user also has to decide which plant gets which amount of fertilizer. To account for the difference in locations and initial weights, "grouping" factors can be defined. When the plants have been properly placed, the user should select the time period for the plants to grow and hit the "Grow" button. The growth and development simulation uses an adapted version of TOMGRO, a well-known growth model for tomatoes (Jones et al., 1991), as well as standard climatic data for the time period selected. This applet allows the user to get comparative experience with almost all classical designs completely randomized, complete or incomplete block, Latin Square, etc. There is also ample opportunity to invent and use new setups, made to accom-modate the specific features of the greenhouse situation.