Topic hub
Descriptive Statistics
Core summaries for describing datasets: mean, median, and mode for center; variance, standard deviation, and range for spread; and skewness for shape.
Empirical Rule in Statistics: 68-95-99.7
Learn the empirical rule in statistics: 68%, 95%, and 99.7% of normal data fall within 1, 2, and 3 standard deviations of the mean. Worked examples included.
Frequency Tables: How to Find Frequency, Build & Read Them
Frequency in statistics is how often a value appears. Build a frequency table step by step, group data into classes, and find relative and cumulative frequency.
How to Calculate Standard Deviation in Excel
Calculate standard deviation in Excel with STDEV.S or STDEV.P, avoid the header-row and hidden-row traps, and check a full worked example.
How to Find Outliers: The 1.5×IQR Rule & Formula
Learn how to find outliers using the 1.5×IQR rule. Covers the outlier formula, step-by-step calculation, and a fully worked example with real numbers.
How to Find the Mean: Average Formula and Examples
How to find the mean step by step: sum the values, divide by the count, and handle zeros, missing data, grouped tables, and averaged averages correctly.
How to Find the Median: Formula & Steps
Learn how to find the median step by step: sort values, apply the median formula, and handle both odd and even data sets with worked examples.
How to Find the Range in Statistics
The range measures spread in one subtraction: largest value minus smallest. Formula, worked examples with real data, and a free range calculator.
Interquartile Range (IQR): Formula & How to Find It
Learn what the interquartile range is, the IQR formula, and how to find it step by step. Includes a worked example, outlier detection, and IQR vs range.
Mean Absolute Deviation & Coefficient of Variation
Mean absolute deviation explained with a worked example, the coefficient of variation, and the real reason standard deviation is the default.
Mean, Median, Mode & Range: The Complete Guide
Learn how to find mean, median, mode, and range with step-by-step examples. Covers what mode means in math, how to calculate each measure, and when to use them.
Median vs Average: What Does Median Mean in Math?
Median vs average explained: learn what median means in math, how to calculate it, and when to use median instead of the mean with clear examples.
Percentiles: Meaning, Definition & How to Calculate
Understand the percentile meaning and definition: the value below which p% of data falls. Covers the formula, a fully worked example, and a free calculator.
Standard Deviation: Meaning, Formula & How to Calculate
Learn what standard deviation means, see the full formula, and follow a worked example to find it for any dataset — sample or population.
The Standard Deviation Symbol (Sigma): Signs & Notation
Learn the standard deviation symbol: σ for population, s for sample. Understand every sign for standard deviation and which symbol identifies each.
Variance: Definition, Sample Variance Formula & vs Standard Deviation
Variance measures how spread out data values are from the mean. Learn the population and sample variance formulas, why n − 1, and how variance differs from SD.
Weighted Average: Definition, Formula & Calculator
A weighted average gives each value a different importance. Learn the weighted average formula, how to calculate it step by step, and when to use it.
What Is an Average? Mean vs Average, Types & Meaning
An average is one number standing in for many. Mean, median and mode each give a different answer, and average doesn't always mean the mean. How to choose.