STUDY THEME 9: Sampling Methods \& Statistical Analysis 18. Define the Null Hypothesis as used in the comparison of two means of two sets of data theoretically belonging to the same population using a two-tailed normal distribution test. Show clearly how you could determine whether two samples determined by quintuplicate measurements belong to the same theoretical population. (16pts) CI.UE 19. Describe the procedure followed to establish the accuracy and sensitivity of a new method proposed for measurement of a certain compound in a laboratory. State how the method is verified nationally and internationally. (12pts) 20. An ion-selective electrode method was compared with a standard iodometric method for determining the concentration of dissolved sulphide in groundwater using the following results from a Blocked test. Evaluate the data and determine whether the electrode method records statistically different values from the iodometric method. ( 12 pts)