WooCommerce Post-Purchase Survey: 7 Questions, When to Ask and What to Do Next Descriptive statistics
Glossary 
Mike Taylor Updated: Nov 11, 2026 Reading time ≈ 3 min
- Topic
- Data analysis and statistics
- Calculator
- Median and percentile calculator
Contents
Descriptive statistics are numbers and charts that summarize the main features of a dataset: its typical value (mean, median, mode), how spread out the values are (range, standard deviation, interquartile range) and how often each value or category occurs (frequencies and percentages). They describe the data you actually collected, without drawing conclusions about a wider population, and they are the first step in analyzing any survey or study.
The opposite branch is inferential statistics: significance tests, confidence intervals and models that use a sample to say something about a population. Descriptive statistics come first, because you need to know what the data looks like before testing anything.
Types of descriptive statistics
| Type | Measures | Question it answers |
|---|---|---|
| Central tendency | Mean, median, mode | What is a typical value? |
| Dispersion (spread) | Range, variance, standard deviation, interquartile range (IQR) | How much do values differ from each other? |
| Frequency distribution | Counts, percentages, cumulative percentages | How often does each answer occur? |
| Shape of the distribution | Skewness, kurtosis, histograms | Is the data symmetric? Are there outliers or several peaks? |
Worked example
Ten customers rate support on a 1–5 scale: 4, 5, 3, 4, 5, 2, 4, 5, 4, 3.
Sorted: 2, 3, 3, 4, 4, 4, 4, 5, 5, 5.
- Mean = 39 ÷ 10 = 3.9
- Median = average of the 5th and 6th values = (4 + 4) ÷ 2 = 4
- Mode = 4 (appears four times)
- Range = 5 − 2 = 3
- Standard deviation (sample) = 0.99. The squared deviations from the mean add up to 8.9; divided by n − 1 = 9 that gives a variance of about 0.989, and its square root is about 0.99.
- Interquartile range = Q3 − Q1 = 5 − 3 = 2, using the median of each half. Software may give slightly different quartiles depending on the method.
| Rating | Count | Percent |
|---|---|---|
| 5 | 3 | 30% |
| 4 | 4 | 40% |
| 3 | 2 | 20% |
| 2 | 1 | 10% |
| 1 | 0 | 0% |
Summary for the report: "Average rating 3.9 out of 5 (median 4, SD 0.99, n = 10); 70% rated support 4 or 5." The standard deviation calculator checks the spread for any list of numbers.
Which statistics fit which data
| Level of measurement | Example | Appropriate statistics |
|---|---|---|
| Nominal | Country, plan, gender | Counts, percentages, mode |
| Ordinal | Rating scales, education level | Plus median, percentiles, IQR |
| Interval and ratio | Age, income, time, number of purchases | Plus mean, standard deviation, range |
Means and standard deviations of rating scales are common in practice, especially for scales that combine several items. For a single rating question, show the distribution or the median as well.
Descriptive vs inferential statistics
| Descriptive | Inferential | |
|---|---|---|
| Goal | Summarize the sample | Generalize to the population, test hypotheses |
| Typical output | "68% of respondents are satisfied" | "Between 63% and 73% of all customers are satisfied (95% CI)" |
| Tools | Means, percentages, charts | t-tests, chi-square, confidence intervals, regression |
Common mistakes
- Reporting a mean without spread. "Average 3.5" can mean everyone answered 3 or 4, or that answers split between 1 and 5.
- Calculating means of categories, such as the average of region codes.
- Leaving out n. Percentages from 12 answers and from 1,200 answers look the same in a chart.
- Using the mean for skewed data like income or completion time, where the median is more representative.
- Treating descriptive differences as proof. "Group A scored 4.2 and group B 3.9" is a description. Whether the difference is real needs an inferential test.
How to describe survey data
- Check the data first: number of responses, missing answers, duplicates, speeders.
- Build frequency tables for every closed question.
- For numeric and scale questions, calculate the mean, median and standard deviation, and look at a histogram for skew and outliers.
- Break the key figures down by segment (cross-tabulation), stating n for each group.
- Only then move to tests and models.
For Rating questions, the SurveyNinja report already shows the mean, median and standard deviation.
A step-by-step walkthrough with survey examples is in How to do descriptive analysis on survey data.
Updated: Nov 11, 2026 Published: May 31, 2026