A hypothesis test is conducted to test whether the mean age of clients at a certain health spa is equal to 25 or not. It is known that the population standard deviation of clients at the spa is 10. 36 clients are randomly selected, and their ages recorded, with the sample mean age being 27.8. What is the test statistic of the hypothesis test in this case?

Econometrics is an application of statistical methods to economic data in order to give empirical content to economic relationships.  Basically, it is "the quantitative analysis of actual economic phenomena based on the concurrent development of theory and observation, related by appropriate methods of inference". (Source: Wikipedia)

Econometrics relies on techniques such as regression models and null hypothesis testing. Econometrics can also be used to try to forecast future economic or financial trends.