A time-series data shows information about the** same** subject or element of a sample or population for **different** periods of time.

The information in the table below is not based on **real** statistical data, but it can help us understand what we mean by time-series data.

The table below shows time-series data for the following two reasons:

First, you can see that the information is about the **same subject** that is **numbers of cars rented by Alamo**.

Second, the information is given for **different time period**. From year 2000 to year 2004.

Notice that a time-series data could also be compiled by using month as a time frame instead of year.

For instance, you could compile information from January to December.

In summary, a set of data is a time-series data whenever the following two conditions are met.

- The information is about the same subject

- The information is for different time period