Box and whisker plots
Box Plot Maker: Box and Whisker Plots Online
Make a box and whisker plot for up to three data sets on one axis, with outliers marked by the 1.5 × IQR rule and a five-number summary table. Download as SVG.
| Data set | Min | Q1 | Median | Q3 | Max | Outliers |
|---|---|---|---|---|---|---|
| Class A | 62 | 72.5 | 79 | 86.5 | 97 | — |
| Class B | 55 | 68 | 74.5 | 82.5 | 99 | — |
Every value is calculated in your browser from the standard normal distribution (Marsaglia’s series for Φ) and rounded to four decimals; the tables were checked cell by cell against an independent calculation. These tables give the area to the left of z. Some textbooks, including the NIST handbook, print the area from 0 to z instead, which is the left area minus 0.5 for positive z.
Reading a box plot
The box runs from Q1 to Q3 and the line inside it is the median. The whiskers reach the smallest and largest values that are not outliers, and outliers are drawn as open circles. Plotting groups on one axis makes it easy to compare their centers and spreads.
- Leave a data set empty to plot fewer groups.
- The quartile method changes Q1 and Q3 slightly for small data sets.
Common questions
What does a long whisker mean?
The values on that side are spread out more widely, which often means the data are skewed in that direction.
Can I compare two classes?
Yes. Enter each class as its own data set; all plots share one scale so they can be compared directly.
The studio notebook
A useful place to begin.
Clear steps, considered details, and ideas you can put to use.
How to Read a Z Table (Left-Tail Areas, Step by Step)
Learn to read a standard normal z table: find the row and column, get left-tail, right-tail and between-two-values areas, and handle other table layouts.
Z-Score Formula and Worked Examples
Use the z-score formula z = (x − μ) / σ, read what the sign and size mean, convert a z-score to a percentile, and handle sample means with σ/√n.
Sample vs Population Standard Deviation (n vs n − 1)
Know when to divide by n and when to divide by n − 1, with the formulas, a worked data set, the link to variance, and the mistakes that cost points.
Mean, Median and Mode: Definitions, Examples and Which to Use
Find the mean, median and mode of a data set, see how one outlier moves each one, and decide which measure of center to report for your data.
T Table vs Z Table: Which One to Use and How to Read It
Decide between the t table and z table, find degrees of freedom, read one-tailed and two-tailed columns, and see why t values approach z as df grows.
How to Read a Chi-Square Table (df, Critical Values, p-Values)
Find degrees of freedom for goodness-of-fit and independence tests, read right-tail critical values, and compare them with your chi-square statistic.