Descriptive statistics calculators
Standard Deviation Calculator
Sample and population SD with the full deviation table.
Variance Calculator
Sample and population variance with sum of squares.
Mean, Median & Mode
All three averages, compared side by side.
Mean Calculator
The average, with sum and count shown.
Median Calculator
The middle value, with sorted data.
Quartile Calculator
Q1, median and Q3 (QUARTILE.INC method).
IQR Calculator
Interquartile range and outlier fences.
Five Number Summary
Min, Q1, median, Q3, max. Box-plot ready.
Descriptive Statistics
The complete summary in one paste.
More descriptive tools
Mode Calculator
The most frequent value, ties included.
Average Calculator
The plain mean, audited.
Weighted Average
For grades, GPA and portfolios.
Geometric Mean
The right average for growth.
Harmonic Mean
The right average for rates and speeds.
Range Calculator
Max minus min, with its limits.
Midrange Calculator
The midpoint of the extremes.
Percentile Calculator
Any percentile of your dataset.
Percentile Rank
The rank of one score inside its group.
Decile Calculator
D1 to D9 cut points, plus a value locator.
Outlier Calculator
Tukey fences and flagged values.
Standard Error
The precision of a sample mean.
Coefficient of Variation
Spread as a percentage of the mean.
Mean Absolute Deviation
The average distance from the mean.
Median Absolute Deviation
The outlier-proof spread.
Sum of Squares
The total behind every variance.
Frequency Table
Counts, percentages, cumulative totals.
Shape, association & the normal model
Statistics Calculator
The all-in-one dataset summary.
Skewness Calculator
Measure and read asymmetry.
Kurtosis Calculator
Excess kurtosis and tail weight.
Covariance Calculator
Co-movement, with correlation.
Degrees of Freedom
For t, chi-square and correlation.
Pooled Standard Deviation
Combined spread of two groups.
Pooled Variance
The weighted combined variance.
Grouped Data Mean
Estimated mean from a frequency table.
Lower & Upper Fences
Tukey's outlier boundaries.
Normal Distribution
P(X < x) from mean and SD.
Empirical Rule
The 68–95–99.7 ranges.
Raw Score Calculator
Z-score back to a raw value.
Z-Score Probability
Areas below and above any z.
Z-scores, percentiles & tables
Z-Score Calculator
Z-score with percentile and interpretation.
Z-Score to Percentile
Convert z to percentile exactly.
Percentile to Z-Score
Inverse normal conversion for cut-offs.
Z Table
The full standard normal table, with examples.
Inverse Normal Distribution
Area in, z or raw score out: left, right or central.
T-Score Calculator
T = 50 + 10z, from raw scores or z directly.
Stanine Calculator
The nine standard bands, with the full table.
Regression & correlation
Correlation Calculator
Pearson r with the scatter plot beside it.
Linear Regression
Slope, intercept, equation, residuals, predictions.
R-Squared Calculator
From paired data, or straight from r.
Spearman Correlation
Rank correlation, ties handled.
Multiple Regression
Up to five predictors, full coefficient table.
Quadratic Regression
Fit a parabola, compare it with the line.
Exponential Regression
Growth rate, doubling time, half-life.
Logistic Regression
Yes-or-no outcomes, odds ratios, the S-curve.
Line of Best Fit
The least squares line, equation first.
Regression Equation
y-hat = a + bx, with fitted values and residuals.
Correlation Coefficient
What r is, how it is built, how to read it.
Chart makers
Histogram Maker
Paste data, choose bins, see the shape.
Box Plot Maker
Five numbers and outliers, drawn.
Scatter Plot Maker
Paired data with an optional trend line.
Bar Chart Maker
Label and value rows, zero-baseline axis.
Pie Chart Maker
Shares, percentages and slice angles.
Dot Plot Maker
Every value on the number line.
Stem and Leaf Plot
The chart you can rebuild the data from.
Line Graph Maker
Time series from label and value rows.
SD Graph Calculator
Mean and SD bands on your histogram.
Normal Graph Calculator
Fit the bell curve to your data.
Probability, counting & sampling
Odds Calculator
Probability to odds and back, decimal included.
Coin Flip Probability
Exactly, at most or at least k heads in n flips.
Dice Probability
Sums for 1 to 6 dice, fully tabulated.
Random Number Generator
Uniform draws, duplicates on or off.
Permutations & Combinations
Both counts side by side, repetition included.
Combinations with Repetition
Stars and bars: C(n + r - 1, r).
Geometric Distribution
Trials until the first success.
Hypergeometric Distribution
Sampling without replacement, exactly.
Negative Binomial Distribution
Trials until the r-th success.
Normal Approximation to Binomial
With the continuity correction, errors shown.
Slovin's Formula
Sample size from N and a margin e.
Cochran's Formula
Sample size with z and p chosen openly.
Finite Population Correction
Shrink n0 to fit a finite list.
Response Rate
Response, start and completion rates kept apart.
Statistical tables
T Table
Critical t values, df 1 to 120 and infinity.
Chi-Square Table
Right-tail critical values, df 1 to 30.
F Table
Critical F values at 5% and 1%.
Correlation Critical Values
The smallest significant r for each n.
Learning guides
All Learning Guides
Thirty plain-language guides with worked examples.
Which Test Should You Use?
The decision table: question and data in, test out.
What Is a P-Value?
The definition, and the three classic misreadings.