I. The data used in this example were collected in southern Florida between 1968
ID: 3126496 • Letter: I
Question
I. The data used in this example were collected in southern Florida between 1968 and 1972 to determine whether injection of silver sodide into cumulus clouds (cloud seeding) tends to increase rainfall. Fifty-two days when weather conditions were suitable for cloud seeding were randomly divided into two groups of 26 days. For one group of 26 days the target cloud was injected with silver iodide (the target cloud was seeded). For the other group of 26 days the target cloud was not injected with silver iodide (the target cloud was not seeded). For each of the 52 days, the total amount of rainfall was mensured. The unit of measurement for the amount of ranfall is acre feet. (One acre foot of rain is the tends to increase rainfall. Fifty-two days when weather conditions were s volume needed to cover one acre to a depth of one foot.) Cloud seeding data (rainfall amounts in acre-feet) seeded days 4.1 7.7 17.5 31.4 32.7 40.6 92.4 115.3 118.3 119.0 129.6 198.6 200.7 242.5 255.0 274.7 274.7 302.8 334.1 430.0 489.1 703.4 978.0 1656.0 1697.8 2745.6 unseeded days 1.0 4.9 4.9 11.5 17.3 21.7 24.426.1 26.3 28.6 29.0 36.6 411 47.3 68.5 81.2 87.0 95.0 147.8 163.0 244.3 321.2 345.5 372.4 830.1 1202.6 Summary statistics seeded unseeded min4.1 01 92.4 med 221.6 3 430.0 max 2745.6 range 2742 IQR 337.6 min 1.0 01 24.4 med 44.2 Q3 163.0 max 1202.6 range 1202 IQR 138.6 mean 441.98 std. dev. 650.79 mean 164.59 std dev. 278.43Explanation / Answer
(C)
As the sample size is same for both the class, then we can compare the two means. We see that for the first class mean is much higher than the 2nd class. But we will not claim the difference in the location paramenters just by seeing the means, we have the see the median also. We see that both the mean and median of the seeded days are significantly higher than that of unseeded days respectively. The ratio of the mean of the two class is 441.98/164.59 = 2.68 > 1 and that of median is 221.6/44.2 =5.01 >> 1 And the Range of the values for the seeded days is much higher than that of unseeded days. So We can conclude that the location or the central tendency parameters of the seeded days is significantly greater than the unseeded days.
(D) Regarding the variability of the two class we will look at the Standard deviation value, range Value and the IQR Value. The ratio of the standard deviation and IQR value the seeded and unseeded days are respectively 650.79/278.43= 2.34 > 1and 337.6/138.6 =2.44 > 1 and the same scenarion for the range value also. So we can conclude that the value of the seeded days are more sparsed than that of unseeded days. So the Variability of the seedded days value is much higher than that of unseeded days.