Disclaimer

TableSigma’s tables and calculators, starting with the interactive TableSigma z table, are reference and study aids. This page explains the limits of what they can tell you.

Rounding and precision

Every value on TableSigma is generated live from the relevant distribution’s cumulative function (standard normal, Student’s t, or chi-square) and displayed rounded to four decimal places, which matches the precision of a standard printed textbook table. Statistical software usually carries more decimal places internally, so a side-by-side comparison can show a difference in the fifth or sixth digit — not a disagreement, just more digits shown.

For example, TableSigma’s z table shows P(Z ≤ 1.96) = 0.9750. In Excel, the formula =NORM.S.DIST(1.96,TRUE) returns 0.975002 — the same probability, carried two digits further. Rounded to four decimal places, both agree exactly. If you need more than four decimal places for a specific calculation, use statistical software directly rather than reading extra precision into a rounded table.

Not a substitute for your textbook or instructor

These tools are built to speed up a lookup you already understand how to do, not to replace learning the method. If a result does not match what your course expects, check your degrees of freedom, tail selection (one- vs two-tailed) and rounding convention before assuming the table is wrong — and ask your instructor if you are still unsure.

Not for medical, financial or legal decisions

TableSigma is built for academic statistics coursework and general reference. It is not intended for, and should not be used as the basis for, medical, clinical, financial or legal decisions. For those, consult a qualified professional using validated tools appropriate to that field.

Advertising

If display advertising is ever shown on this site, it has no effect on the table values or calculator results — every number is computed independently from the distribution formula, not influenced by ads or sponsorships.

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