The mean yield of wheat from a district A was 210 kg with standard deviation 10 kg per

acre from a sample of 100 plots. In another district B, the mean yield was 220kg with

standard deviation 12 kg from a sample of 150 plots. Assuming that the standard

deviation of the yield in the entire state was 11kg, test whether there is any significant

difference between the mean yields of crops in the two districts.