Vendor-file audit sample size calculator
Cochran sample with finite-population correction, 95% CI (z=1.96). Use p=0.5 when you do not know the defect rate.
Sample size for vendor credentialing file audits
Vendor credentialing and compliance teams often audit a random sample of vendor files rather than every file. This calculator estimates how many files to pull for a 95% confidence level, using Cochran’s sample-size formula with a finite-population correction. Browse the free tools hub for related checks.
How to use this sample size calculator
Enter the number of active vendor files (N), the expected defect rate (p), and the margin of error (e). Use p = 0.5 if you do not know the defect rate. Pull that many files at random, and stratify by high-risk roles if your SOP says so. Then review what you pull with the background-check recency checker, the COI coverage gap checker, and the training recency tracker.
Calculate your sample
197 files
Pull that many at random. Stratify by high-risk roles if your SOP says so.
How to read the result
The result is the number of files to review to estimate the defect rate within ± e at 95% confidence. With the defaults — 400 files, p = 0.5, e = 0.05 — the calculator returns 197 files. A smaller margin of error or a larger file count raises the sample.
Sample sized — next is running vendor-file audits on a regular cadence and fixing what they find. Talk to a pilot team about operationalizing it at your hospital or ASC.
FAQ
- How does this sample size calculator work?
- It uses Cochran’s formula at 95% confidence (z = 1.96): n₀ = z² × p × (1 − p) ÷ e². It then applies a finite-population correction, n = n₀ ÷ (1 + (n₀ − 1) ÷ N), and rounds up to a whole file.
- What defect rate should I enter?
- If you have a defect rate from a previous audit, use it. If not, use 0.5: p × (1 − p) is largest at 0.5, so it gives the most conservative sample size.
- What margin of error should I use?
- The margin of error is how close you want the audit’s defect rate to be to the true rate. The default 0.05 means within 5 percentage points. Use what your SOP or compliance lead requires; a smaller margin needs more files.
- Does the sample need to be random?
- Yes. The formula assumes a random sample. If your SOP calls for extra scrutiny of high-risk roles, such as reps with sterile-field access, stratify the files and draw at random within each group.
- Is this a substitute for our audit procedure?
- No. It is an educational calculator for vendor credentialing and compliance staff. Your audit SOP and compliance lead decide the sampling method and confidence level.
Educational only. Not a credentialing determination, not legal advice, and not a substitute for each facility’s policy. Vendor-file audit sample size calculator does not submit files to hospitals or GHX/Vendormate/Symplr.