If the hypothesis was not correct, they develop a new hypothesis and test it again. Sometimes a scientist will think his or her hypothesis is correct and then after a while new information will come along and their hypothesis will no longer be correct. In order to test your hypothesis, make a prediction about what you will find when you look at the data, assuming your hypothesis to be true. Americans use more water than Europeans. The average amount of water used by all American classes will be greater than the average amount of water used by all European classes.
Water usage depends on geographical location.