12. 150 randomly selected cows were tested for flue bacteria. It was found that 18 of the cows showed such bacteria. Test the hypothesis that more than 10% of the flock of cows has been infected. (Use a 5% level of significance). 13. A random sample of 10 hot drinks from Dispenser #1 a mean volume of 203 ml and a standard deviation 3 ml. A random sample of 15 hot drinks from Dispenser #2 gave corresponding values of 206 ml and 5 ml. The amount dispensed by each machine may be assumed to be normally distributed. Test, at 10 % significance level, the hypothesis that there is no difference in the variability of the volume dispensed by two machines