4.5.15. Snedecor and Haber (1946) presented data on cutting dates of asparagus.

On two plots of land, asparagus was grown every year from 1929 to 1938. On the first plot the asparagus was cut on June 1, while on the second plot the asparagus was cut on June 15. Note that growing conditions will vary considerably from year to year. Also note that the data presented have cutting dates confounded with the plots of land. If one plot of land is intrinsically better for growing asparagus than the other, there will be no way of separating that effect from the effect of cutting dates. Are the data two independent samples or a paired comparison? Give a 95%confidence interval for the difference in populationmeans and give an approximate P value for testing that there is no difference between population means. Give a 95% prediction interval for the difference in a new year. The data are given in Table 4.14.