5.1 - Introduction to Inferences

The real power of statistics comes from applying the concepts of probability to situations where you have data but not necessarily the whole population. The results, called statistical inference, give you probability statements about the population of interest based on that set of data.

Types of Statistical Inference

There are two types of statistical inferences: Estimation and Statistical Tests.


Use information from the sample to estimate (or predict) the parameter of interest.

For instance, using the result of a poll about the president's current approval rating to estimate (or predict) his or her true current approval rating nationwide.

Statistical Tests

Use information from the sample to determine whether a certain statement about the parameter of interest is true. Statistical tests are also referred to as hypothesis tests.

For instance, suppose a news station claims that the President’s current approval rating is more than 75%. We want to determine whether that statement is supported by the poll data.