Fertilization of bromeliads. Does the type of fertilization have a significant effect on leaf development for bromeliads? Researchers compared leaf production and death over a seven-month period for a control group (C), a group fertilized only with nitrogen (N), a group fertilized only with phosphorus (P), and a group that received both nitrogen and phosphorus (NP).17 In the nitrogen and phosphorus columns in the data file, 0 indicates no fertilization and 1 indicates fertilization. The "new" and "dead" columns give the total number of new or dead leaves produced over the seven months following fertilization. "Change" gives the difference "new" minus "dead."
(a) Figure 29.17 displays the one-way ANOVA table and Tukey pairwise comparisons for the number of new leaves. Are there significant differences among the four group means? List the four group means in order from smallest to largest
FIGURE 29.17:
and give a summary of the Tukey procedure similar to that in Example 29.14.
(b) Give the two-way ANOVA table for the number of new leaves. How do your conclusions from this analysis differ from your conclusion in part (a)?
Example 29.14:
STATE: Corn varieties with altered amino acid content can have advantages in feeding animals. Here is an excerpt from a study that compared normal corn ("norm" in the data file) with two altered varieties called opaque-2 ("opaq") and floury-2 ("flou"). Nine treatments were arranged in a 3 × 3 factorial experiment to compare opaque-2, floury-2 and normal corn at dietary protein levels of 20, 16, and 12%. Corn-soybean meal diets containing either opaque-2, floury-2 or normal corn were formulated so that,
for a given protein level, an equivalent amount of corn protein was supplied by each corn. Male broiler-type chicks were randomly allotted to treatments at 1 day of age. Feed and water were provided ad libitum. Chicks were weighed at weekly intervals until termination of the experiment at 21 days.7
There are 10 chicks in each group. The response variable is the weight in grams after 21 days. Which combinations of corn type and protein content lead to fastest growth?