- ProbabilityAndStatistics -- StatisticalRegularity
- PlanningResearch -- InterpretingStatisticalData -- SummaryStatistics

In general, statistical data can be described as a list of *subjects* or *Units* and the data associated with each of them. Although most research uses many data types for each Unit, we will limit ourselves to just one data item each for this simple introduction.

We have two objectives for our summary:

- We want to choose a StatistiC that shows how different
*Units*seem similar. Statistical textbooks call the solution to this objective, a*measure of CentralTendancy*. - We want to choose another StatistiC that shows how they differ. This kind of statistic is often called a measure of
*StatisticalVariability?*.

When we are summarizing a quantity like length or weight or age, it is common to answer the first question with the **MeaN**, the **MediaN**, or the **MoDe**. Sometimes, we choose specific values from the *CumulativeDistributionFunction?* called **QuanTiles?**.

The most common measures of variability for QuantitativeData? are the VarianCe?, its square root, the StandardDeviation?, the RanGe?, InterQuartileRange?, and AbsoluteDeviation?.

[RABeldin ]