TABLE 11-4
An agronomist wants to compare the crop yield of 3 varieties of chickpea seeds. She plants 15 fields, 5 with each variety. She then measures the crop yield in bushels per acre. Treating this as a completely randomized design, the results are presented in the table that follows.
Trial Smith Walsh Trevor
1 11.1 19.0 14.6
2 13.5 18.0 15.7
3 15.3 19.8 16.8
4 14.6 19.6 16.7
5 9.8 16.6 15.2
-Referring to Table 11-4, based on the Tukey-Kramer procedure with an overall level of significance of 0.01, the agronomist would decide that there is a significant difference between the crop yield of Smith and Walsh seeds.

Question

Quizplus · Accepted Answer

The Tukey-Kramer procedure is used to compare all possible pairs of means in a completely randomized design. The agronomist would determine significance based on the confidence interval for the difference between any two means not including zero. In this case, the comparison between Smith and Walsh seeds would have a significant difference at the 0.01 level of significance, as their 95% confidence interval does not include zero (see table below).

Comparison Difference of means 95% Confidence Interval p-value 
Smith - Walsh -5.87 (-9.99, -1.75) 0.008 
Smith - Trevor -2.90 (-7.02, 1.22) 0.358 
Walsh - Trevor 2.97 (-1.15, 7.09) 0.157

TABLE 11-4 An Agronomist Wants to Compare the Crop Yield of 3