To study the bacteria count in the west basin of Lake Macatawa, 37 samples of water were taken from the west basin and the number of bacteria colonies in 100 milliliters of water was counted. The mean and the standard deviation of the sample were 11.95 and 11.80, respectively, measured in hundreds of colonies.


Required:

Test at 0.05 significance level whether the mean number of colonies in 100 milliliters of water in the west basin is less than 12. Use all 3 approaches.