About
Updated 19 Oct 2026
TableSigma is a set of interactive statistics reference tables — z table, t table, chi-square table and related calculators — built for students and researchers who need a fast, exact lookup instead of flipping through a textbook appendix.
What TableSigma does
Every table on this site computes its values live from the underlying probability distribution function (the standard normal, Student’s t, or chi-square distribution), rather than reproducing a scanned textbook table. Enter a value and the matching row, column and probability are highlighted immediately, with a shaded curve chart and a one-click copy button for the result. Each table also offers a printable, one-page layout, alongside calculators for p-values, z-scores and t-tests.
What TableSigma does not do
TableSigma is a reference and lookup tool, not a tutoring or consulting service. It does not complete homework or assignments on a user’s behalf, and it does not provide medical, clinical or research-design advice. For guidance on applying a statistical test correctly to a specific study, consult a course instructor or a qualified statistician.
How our tables are generated
Every cell is computed in JavaScript directly from the relevant distribution’s cumulative function — the standard normal CDF for the z tables, Student’s t CDF for the t tables, and the chi-square CDF for the chi-square tables — then rounded to four decimal places. Values are spot-checked against the NIST/SEMATECH e-Handbook of Statistical Methods and standard textbook reference tables rather than copied from any single source. Because the numbers are generated from the distribution formula instead of a static lookup, the same engine covers z, t and chi-square values consistently across the site.
Who uses TableSigma
The tables are built for college Stats 101 and AP Statistics students checking a homework calculation, AP Biology students running a chi-square goodness-of-fit test on genetics data, and researchers who want a quick critical-value or p-value cross-check without opening statistical software.
Accuracy
Table values are generated from standard numerical approximations of each distribution’s cumulative function, consistent with the methods documented in the NIST/SEMATECH e-Handbook of Statistical Methods. Worked examples on each page are checked against known reference values before publication. If a value ever looks wrong, the “Report an error” form on each table page goes directly to the team that maintains the site.
Who maintains this site
TableSigma is maintained by the TableSigma editorial team. Content and tool behavior are reviewed as part of ongoing upkeep of the site; corrections reported through the table pages are read and addressed by the same team. For the full interactive z table, visit the TableSigma homepage.
Contact
For questions, corrections or anything else, see the Contact page.
FAQ
How accurate are the table values?
Each value is computed from the distribution’s cumulative function and rounded to four decimal places, which matches or exceeds the precision of a standard printed textbook table. Worked examples are checked against the NIST/SEMATECH e-Handbook before publication.
What is the difference between a one-tailed and two-tailed value?
A one-tailed value covers the probability on one side of a cutoff (for example, P(Z > z)); a two-tailed value splits that probability between both ends of the distribution. Each calculator on TableSigma lets you choose which one you need.
Can I download a free PDF copy of the tables?
Yes — the z table page and the dedicated PDF page offer a print-ready layout; use your browser’s “Save as PDF” option in the print dialog to download a copy for personal or classroom use.