Statistics calculators that show their work.
Free calculators for intro college statistics. Every answer comes with a plain-English interpretation, the steps behind it, and the matching TI-84 command.
Descriptive
Summarize and graph a set of data.
- Random SamplePick random whole numbers for a simple random sample, like randInt on the TI-84.
- Frequency Table & HistogramGroup data into classes and get frequencies, relative frequencies, and a histogram.
- 1-Var StatsMean, standard deviation, five-number summary, and more from a list of data, just like STAT → CALC → 1-Var Stats.
- Boxplot & OutliersFive-number summary, IQR, outlier fences, and a modified boxplot.
- Z-ScoresFind a z-score from a value, or a value from a z-score, and check whether it's unusual.
- PercentilesFind the value at the kth percentile, or the percentile rank of a value.
- Weighted MeanWeighted averages such as GPAs and course grades.
- Empirical Rule & Chebyshev68–95–99.7 intervals for bell-shaped data, and Chebyshev's minimum percentages for any shape.
Probability
Counting rules and discrete probability distributions.
- Counting (nPr, nCr)Factorials, permutations (nPr), and combinations (nCr), with exact answers.
- Discrete DistributionMean (expected value), variance, and standard deviation of a probability table.
- BinomialP(X = x), at most, at least, and between, with binompdf and binomcdf commands.
- PoissonProbabilities for counts of events in an interval, with poissonpdf and poissoncdf.
- GeometricProbability the first success happens on trial x, with geometpdf and geometcdf.
Distributions
Areas and cutoffs under normal, t, χ², and F curves.
- NormalShaded-area normal probabilities (normalcdf) and cutoffs (invNorm) for any mean and standard deviation.
- Sampling Distribution (CLT)Probabilities for a sample mean x̄ using σ/√n.
- t-DistributionAreas (tcdf) and critical values (invT) for Student's t-distribution.
- Chi-Square DistributionAreas (χ²cdf) and critical values for the chi-square distribution.
- F-DistributionAreas (Fcdf) and critical values for the F-distribution used in ANOVA.
Inference
Confidence intervals and hypothesis tests for means and proportions.
- CI for a MeanZInterval (σ known) or TInterval (σ unknown) from data or summary statistics.
- CI for a Proportion1-PropZInt: a confidence interval for a population proportion p.
- Sample SizeHow large a sample you need for a desired margin of error.
- Z-Test (mean)Hypothesis test for a mean when σ is known, with shaded p-value and critical values.
- T-Test (mean)Hypothesis test for a mean when σ is unknown, from data or summary statistics.
- 1-Prop Z-TestHypothesis test for a population proportion (1-PropZTest).
- 2-Sample T-TestCompare two independent means (2-SampTTest and 2-SampTInt).
- Paired T-TestMatched pairs (before/after) test on the differences.
- 2-Prop Z-TestCompare two population proportions (2-PropZTest and 2-PropZInt).
Chi-Square & ANOVA
Tests for categorical data and for comparing several means.
Regression
Relationships between two quantitative variables.