CHISQ.INV in Collabora Office: Find a Left-Tail Chi-Square Quantile
Use Collabora CHISQ.INV to convert cumulative probabilities into chi-square thresholds and keep lower-tail and upper-tail conventions distinct.
Verification status: See the evidence and test scope described in this guide. How formula examples are checked
Quick answer: =CHISQ.INV(0.95;2) has independently expected result approximately 5.991464547. It is the threshold with 95% of the two-degree chi-square distribution below it.
Syntax and probability direction
=CHISQ.INV(Probability; DegreesFreedom)
Probability is a left-tail cumulative probability. DegreesFreedom identifies the chi-square distribution. Both are required. Use an interior probability 0<p<1 and positive integer degrees of freedom for the finite examples here.
The output is a chi-square value, not another probability. A request for a 5% upper-tail critical value uses p=0.95 in this function, or p=0.05 in CHISQ.INV.RT. Confusing those directions can move a threshold from one end of the distribution to the other.
The dedicated Collabora help explicitly calls this the inverse left-tailed probability. Its displayed example uses a decimal comma in 0,5; this guide uses the numeric value 0.5 with English formulas and semicolon argument separators.
Example 1: build a percentile table
Put 0.05, 0.5 and 0.95 in A2:A4. Enter =CHISQ.INV(A2;2) in B2 and fill down. Independent thresholds are approximately 0.102586589, 1.386294361 and 5.991464547.
The thresholds increase as cumulative probability increases. The median is approximately 1.386294361; it is not the mean of two for this right-skewed distribution.
For two degrees of freedom, the independent inverse formula is =-2*LN(1-A2). Put that in C2 and fill down as an algebraic reference. This closed form is specific to this degree choice, not a formula for every chi-square quantile.
Example 2: check the forward cumulative value
In D2 enter =CHISQ.DIST(B2;2;1) and fill down. Independent targets are 0.05, 0.5 and 0.95, matching A2:A4.
Use the actual B cell values, not their rounded displayed text. Changing the forward function’s final flag to zero would evaluate a density and would not recover the original probability.
At the 95th-percentile threshold, =CHISQ.DIST.RT(B4;2) instead targets 0.05. This provides a second check that the lower and upper tails have been paired correctly.
Advanced application: reproduce the official median example
=CHISQ.INV(0.5;1) has independently expected result approximately 0.454936423, matching the dedicated help. It differs from the two-degree median because degrees of freedom change the reference distribution.
Do not reuse a threshold from a table with the wrong degree count just because its probability matches. Store the degrees of freedom in a labeled parameter cell and use an absolute reference when filling a quantile column.
Advanced application: express a central probability band
For two degrees of freedom, the fifth and ninety-fifth percentiles bound a central 90% model interval. Its endpoints are approximately 0.102586589 and 5.991464547.
Subtracting CHISQ.DIST at the lower endpoint from its value at the upper endpoint gives an independent target of 0.9. The interval is not symmetric around the mean or median, because the distribution is skewed.
A model interval for a chi-square variable is not automatically a confidence interval for another quantity. Such an interval requires the correct statistical derivation, including how that quantity relates to the chi-square statistic.
Errors and troubleshooting
Use probabilities as fractions or percentage literals: 95% is 0.95, while the bare number 95 is outside the probability scale. Endpoint limits and the application’s native endpoint/error behavior are not certified by these interior examples.
Check whether the requested probability is left-tail or right-tail before editing the degrees of freedom. The dedicated section does not specify every fractional-degree conversion, numeric limit or native error message. Independent round trips verify the mathematical model and argument mapping, not an installed application’s complete accuracy guarantees.
Availability and verification
The exact function is documented in Collabora Office 26.04 desktop help. Its source snapshot was retrieved on 2026-10-13 and hash-verified on October 15, 2026. Desktop documentation does not establish Online or mobile support. First introduced release and last functioning version are unknown; the dedicated source does not establish them.
No native Collabora Office run occurred. All worked values are independent mathematical expectations, not verification of native error codes or every numerical limit. Formulas use English names and semicolon separators.
The help identifies namespace COM.MICROSOFT.CHISQ.INV and places the function outside the cited OpenFormula 1.3 standard. This format disclosure does not prove identical behavior in another product.