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Concept

Descriptive Statistics vs. Inferential Statistics

The study of statistics includes two main branches. One branch, descriptive statistics, allows for data to be described through organizing, summarizing, and displaying it. The purpose of describing the data is to make it understandable for people who will read it. The following are the most common ways to describe data collected from a sample.
Describing Data Collected From a Sample
Calculating the measures of center Mean, median, and mode
Calculating the measures of spread Range, interquartile range, mean absolute deviation, standard deviation, and variance
Representing data graphically Bar chart, pie chart, histogram, frequency polygon, or box plot
Describing the sample probability distribution Represented by tables, equations, or graphs

The other branch of statistics is called inferential statistics. This involves making one or multiple hypothesis, drawing conclusions, predictions, inferences, or generalizations about a population. This is done using data collected from samples. Below are the main areas of inferential statistics.

Making Predictions or Generalizations About a Population
Estimating Parameters Using a statistics from sample data (e.g. the sample mean) to make an estimation about a population parameter (e.g. the population mean). Estimations are commonly presented as confidence intervals.
Hypothesis Tests Using sample data to test if a claim about the mean of a population is true or false.

Example: Descriptive, Inferential, or Both?

A few weeks before a city's election for its next mayor, a company surveyed randomly-selected residents. The residents were asked which candidate they plan to vote into office. The results are represented in the following pie chart.

The chart shows that more than half of the sample participants plan to vote for Candidate A. According to the previous table, this analysis meets the criteria for descriptive statistics. Additionally, based on the sample, it can be inferred that more than half of residents of the city will vote for Candidate A. This is an inference, and therefore, considered to be an inferential statistic.