SB 326 sample size calculator
How many balconies must be inspected.
Civil Code § 5551(a)(4) defines a statistically significant sample as 95% confidence with a margin of error no greater than ±5%. Health & Safety Code § 17973 requires at least 15% of each type. Queries look like this because inspection firms write blog posts, not calculators.
Count each type separately
SB 721 samples at least 15% of each type. SB 326 requires a random 95% / ±5% sampling design (Civ. Code § 5551(a)(4), (c)). This calculator estimates that design per type. A qualified inspector determines the final sample; do not blend balconies and stairs into one N.
The 95 / ±5 formula
n₀ = 1.96² × 0.5 × 0.5 / 0.05² ≈ 384.16; n = n₀ / (1 + (n₀ − 1) / N), rounded up, capped at N.
Cochran n₀ for a proportion, p = 0.5 (maximum variance), Z = 1.96, e = 0.05, then finite population correction. Section 5551 sets a confidence and margin-of-error standard; it does not prescribe this formula. Confirm the design with the qualified inspector.
| N (one type) | SB 326 sample | % of N | SB 721 15% | % of N |
|---|---|---|---|---|
| 8 | 8 | 100% | 2 | 25% |
| 12 | 12 | 100% | 2 | 17% |
| 16 | 16 | 100% | 3 | 19% |
| 24 | 23 | 96% | 4 | 17% |
| 36 | 33 | 92% | 6 | 17% |
| 48 | 43 | 90% | 8 | 17% |
| 60 | 53 | 88% | 9 | 15% |
| 80 | 67 | 84% | 12 | 15% |
| 100 | 80 | 80% | 15 | 15% |
| 150 | 109 | 73% | 23 | 15% |
| 200 | 132 | 66% | 30 | 15% |
| 300 | 169 | 56% | 45 | 15% |
| 500 | 218 | 44% | 75 | 15% |
| 800 | 260 | 33% | 120 | 15% |
| 1200 | 292 | 24% | 180 | 15% |
SB 721 sets a minimum of 15% per type; a larger sample is allowed. For SB 326, a percentage alone does not establish the required statistical confidence.
Not legal advice. Confirm the current statute text on leginfo.legislature.ca.gov and the current filing desk on the city’s .gov site before you send a report or a demand letter.