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 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: Formula & Steps
How to find the mean: sum every value, divide by the count, handle zeros and missing data correctly, and check your answer with a free mean calculator.
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
How to find the range in statistics: subtract the minimum from the maximum, with worked examples and a free range calculator.
Interquartile Range: IQR Formula & How to Find It
Learn what the interquartile range is, the IQR formula (Q3 minus Q1), and how to find it step by step with a worked example and a free calculator.
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
Mean median mode range are the four core statistics for summarizing data: step-by-step formulas, a worked example, and when to use mean, median, or mode.
Median vs Average: What Median Means
Median vs average: the mean sums and divides by count, while the median finds the sorted middle value. Compare both with formulas and worked examples.
Percentile Meaning: Definition & Formula
The percentile meaning in statistics: the value below which a given percent of a data set falls. Covers the definition, formula, and a worked example.
Standard Deviation Excel: STDEV.S, STDEV.P & More
This guide to standard deviation Excel formulas compares STDEV.S and STDEV.P, explains STDEVA, and walks through a full worked example and 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 the Average? Mean, Median & Mode
What is the average? It is one number standing in for many, and mean, median, and mode each answer the question differently from the same data.