It has long been a dream of farmers to summon rain when it is needed for their crops. Crop losses to drought have significant economic impact. One possibility is cloud seeding in which chemicals are dropped into clouds in an attempt to induce rain. Simpson, Alsen, and Eden (Techno metrics, 1975) report the results of trials in which clouds were seeded and the amount of rainfall recorded. The authors report on 26 seeded (Group 2) and 26 unseeded (Group 1) clouds. Each group has been sorted in order of the amount of rainfall, largest amount first. Here are two possible tests to study the question of whether cloud seeding works.
Paired t-Test of μ(1 – 2)
Mean of Paired Differences = -277.4
t-Statistic = -3.641 w>25 dfp = 0.0012
2-Sample t-test of μ1 – μ2
Difference between Means = -277.4
t-Statistic = -1.998w>33 dfp = 0.0538
a) Which of these tests is appropriate for these data? Explain.
b) Using the test you selected, state your conclusion.