The effect of acid rain upon the yield of crops is of concern in many places. In order to determine baseline yields, a sample of 13 fields was selected, and the yield of barley (g/400m2) was determined. The output from SAS appears below:

QUANTILES(DEF=4) EXTREMES

N 13 SUM WGTS 13 100% MAX 392 99% 392 LOW HIGH

MEAN 220.231 SUM 2863 75% Q3 234 95% 392 161 225

STD DEV 58.5721 VAR 3430.69 50% MED 221 90% 330 168 232

SKEW 2.21591 KURT 6.61979 25% Q1 174 10% 163 169 236

USS 671689 CSS 41168.3 0% MIN 161 5% 161 179 239

CV 26.5958 STD MEAN 16.245 1% 161 205 392

A 95% confidence interval for the mean yield is:

a.220.2 ± 1.96(58.6)

b.220.2 ± 1.96(16.2)

c.220.2 ± 2.18(58.6)

d.220.2 ± 2.18(16.2)

220.2 ± 2.16(16.2)