What each statistic means
| Statistic | What it tells you |
|---|
| Mean | The average value |
| Median (Q2) | The middle value; half the data is below it |
| Q1 and Q3 | The values a quarter and three quarters of the way through the sorted data |
| IQR | Q3 − Q1: the spread of the middle 50% of the data |
| Standard deviation | The typical distance of a value from the mean |
| Coefficient of variation | Standard deviation as a percent of the mean, for comparing spread across data sets |
| Outliers | Values unusually far from the rest (1.5 × IQR rule) |
Reading the box plot
The box stretches from Q1 to Q3, with a line at the median. The whiskers reach the smallest and largest values that are not outliers, and outliers appear as separate dots. A long whisker or a median off-center tells you the data is skewed.
Example
In the sample data, most values sit between 20 and 33, but 58 is far above the rest. It is flagged as an outlier, and it pulls the mean (about 28) above the median (24.5). When an outlier like this appears, check whether it is a typo or a genuine result before deciding how to handle it.
Only need the basics? Use the mean, median and mode calculator or the variance calculator.
Last reviewed October 2026.
Frequently asked questions
What does this statistics calculator compute?
It gives the count, sum, mean, median, mode, minimum, maximum, range, quartiles (Q1, Q3), interquartile range, sample and population standard deviation and variance, standard error, coefficient of variation, skewness, geometric mean and any outliers.
How are outliers found?
The calculator uses the 1.5 × IQR rule. Any value below Q1 − 1.5 × IQR or above Q3 + 1.5 × IQR is flagged as an outlier. This is the same rule used to draw the whiskers on a box plot.
Which quartile method is used?
Quartiles use the median-of-halves method taught in most US high school and AP Statistics courses: split the sorted data at the median (leaving the median out when the count is odd) and take the median of each half. Spreadsheets sometimes use other methods, so small differences are normal.
What is the standard error of the mean?
The standard error is the sample standard deviation divided by the square root of the count. It estimates how much the sample mean would vary if you repeated the sampling, and it shrinks as your sample grows.
What does skewness tell me?
Skewness describes the shape of the data. Near 0 means roughly symmetric. Positive means a long tail to the right (a few large values), and negative means a long tail to the left.