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API · /samplesize-api

Sample Size API

healthy 3,896 Subscribers

Survey and poll sample-size planning as an API, computed locally and deterministically. The proportion endpoint computes the number of respondents needed to estimate a proportion within a target margin of error at a chosen confidence level, n = z²·p(1−p)/E², defaulting to the worst-case p = 0.5 that maximises the required size, with an optional finite-population correction n/(1 + (n−1)/N) for a known population — the classic ±5 % margin at 95 % confidence needs 385 responses, ±3 % needs 1 068, and capping the population at 1 000 cuts the ±5 % requirement to 278. The mean endpoint sizes a sample for estimating a mean to within a margin of error from the standard deviation, n = (z·σ/E)². The margin endpoint inverts the relationship, returning the margin of error a given sample size actually achieves. The critical z-value is computed from the confidence level with a high-accuracy inverse-normal so any confidence works, not just the textbook 90/95/99 %. Margins, proportions and confidence are decimals (0.05, 0.5, 0.95). Everything is computed locally and deterministically, so it is instant and private. Ideal for market-research, polling, UX-research, survey-platform, product-analytics and statistics-education app developers, study-planning and sample-size tools, and research software. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is sample-size planning with the normal approximation; for A/B-test significance use an A/B-test API and for descriptive statistics a statistics API.

#sample-size #survey #margin-of-error #polling #market-research #developer-tools
api.oanor.com/samplesize-api
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Machine-readable spec so AI agents can integrate this API.

/api/samplesize-api/openapi.json
/api/samplesize-api/llms.txt

Discovery: GET /api/index.json lists every API.

API health

healthy
Uptime
100.00%
Server probes · 24h
Avg latency
87 ms
Server probes · 24h
Subscribers
3,896
active
Total calls
20
last 7 days
status Full status page → · 24 probes/24h

Pricing

Pick a tier — billed monthly, cancel anytime.

Free

Free

  • 6,200 calls / month
  • 2 requests / second
  • Hard cap (429 above quota, no overage)
  • 6,200 calls/month
  • 2 req/sec
  • Proportion + mean + margin of error
  • No credit card
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Starter

€5.60 /month

  • 62,000 calls / month
  • 6 requests / second
  • Hard cap (429 above quota, no overage)
  • 62,000 calls/month
  • 6 req/sec
  • Any confidence level, finite population
  • Email support
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Pro

€15.80 /month

  • 280,000 calls / month
  • 15 requests / second
  • Hard cap (429 above quota, no overage)
  • 280,000 calls/month
  • 15 req/sec
  • Survey-platform & research pipelines
  • Priority support
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Mega

€49.50 /month

  • 1,550,000 calls / month
  • 40 requests / second
  • Hard cap (429 above quota, no overage)
  • 1,550,000 calls/month
  • 40 req/sec
  • Platform scale
  • Dedicated SLA
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Related APIs

Other APIs with overlapping tags.

Statistical Inference API

Inferential-statistics maths as an API, computed locally and deterministically. The samplesize endpoint computes how many respondents a survey or experiment needs for a proportion, n = Z²·p(1−p)/E², from a confidence level and a margin of error (using p = 0.5 for the most conservative size), with a finite-population correction when the population is known. The confidence endpoint builds a confidence interval for a mean (estimate ± Z·σ/√n) or a proportion (p ± Z·√(p(1−p)/n)), returning the standard error, margin of error and the lower and upper bounds. The ztest endpoint runs a one-sample z-test, z = (x̄ − μ₀)/(σ/√n), and returns the z-score, the one- or two-tailed p-value and whether the result is significant at the chosen alpha. The z-scores come from an exact inverse-normal and the p-values from the normal CDF. Everything is computed locally and deterministically, so it is instant and private. Ideal for A/B-testing, survey, research and analytics app developers, experiment dashboards and data-science tools, and education. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is inferential statistics; for descriptive statistics use a statistics API and for probability distributions use a probability API.

api.oanor.com/inference-api

Reptile Husbandry API

Reptile-husbandry maths as an API, computed locally and deterministically — the keeper numbers behind a healthy vivarium, so the setup is right before the animal moves in. The enclosure endpoint turns an animal length and its habit into the minimum floor length, width and height: terrestrial snakes want a floor at least as long as the snake (a 48-inch corn snake → a 48 × 24 × 24 inch minimum, eight square feet of floor), arboreal species trade floor for height (an 18-inch chameleon → 27 × 18 × 36 inches, tall), and ground lizards and tortoises need far more floor than their body length. The uvb endpoint gives the UV-B target by Ferguson zone — the 1-to-4 classification from Baines et al. (2016) of how much sun a species basks in — returning the mean and basking UV-index ranges (zone 3 open baskers want a basking UVI of 2.9–7.4), and, if you pass a lamp UVI measured at a reference distance, an inverse-square estimate of the mounting distance for the right basking UVI. The feeding endpoint sizes prey from body weight and life stage: a meal of roughly 10–15 % of body weight, no wider than the animal, on an interval that lengthens with age — a 500 g adult snake takes a 40–60 g prey item every fortnight. Everything is computed locally and deterministically, so it is instant and private. Ideal for reptile-keeper and herpetoculture apps, pet-store and breeder tools, vivarium-planning calculators, and care-sheet sites. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 compute endpoints. Educational husbandry estimates — not veterinary advice; research your exact species.

api.oanor.com/reptile-api

Garden Pond API

Garden and koi-pond maths as an API, computed locally and deterministically — the numbers behind a backyard water feature, so you do not have to guess at the hose. The volume endpoint turns length, width and average depth into the water volume in cubic feet, US gallons and litres, applying a shape factor (rectangular 1.0, oval or round 0.79, irregular 0.85) because a liner pond never holds the full bounding box: an 8 × 6 ft pond two feet deep is about 96 cubic feet, or 718 gallons. The liner endpoint sizes the flexible liner to fit a pond — length equals the pond length plus twice the maximum depth plus twice the overlap to anchor under the edging stones (same for width), so that same 8 × 6 pond at two feet deep with a one-foot overlap needs a 14 × 12 ft liner and matching underlayment. The stock endpoint turns a water volume into a safe fish load and the pump you need: roughly one koi per 250 gallons (they grow large and dirty) or one goldfish per 20, plus the pump flow in gallons per hour to turn the whole pond over at least once an hour for koi — 718 gallons holds about two koi and wants a ~720 GPH pump before head-height losses. Everything is computed locally and deterministically, so it is instant and private. Ideal for landscaping and pond-installer tools, garden-design and home-improvement apps, koi and water-garden hobbyist sites, and aquascaping calculators. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 compute endpoints. For pool chemistry use a pool API; for indoor fish tanks use an aquarium API.

api.oanor.com/pond-api

Sunscreen & UV API

Sun-safety maths as an API, computed locally and deterministically — the burn-time, SPF and reapplication numbers a sunscreen, weather or outdoor app keeps people safe with. The burntime endpoint estimates how long until sunburn from the Fitzpatrick skin type (1 very fair to 6 deeply pigmented), the UV index and the SPF: unprotected time is a skin-type base (type II around 15 minutes) scaled by 6 ÷ UV index, and protected time is that times the SPF — so fair type-II skin at UV 8 burns in about 11 minutes bare, or roughly 5½ hours under SPF 30, while very fair type-I skin in extreme UV 11 burns in 5 minutes. The spf endpoint flips it: the SPF needed = your desired minutes outdoors ÷ the unprotected time, with the reminder that real protection plateaus around SPF 30–50. The amount endpoint covers the part people get wrong — about 2 mg/cm², roughly 1 ounce (30 g, a shot glass) for a full adult body, reapplied every two hours — and totals the sunscreen for a day out. Everything is computed locally and deterministically, so it is instant and private. Ideal for sun-safety, weather, skincare and outdoor app developers, UV-alert and reminder tools, and wellness software. Pure local computation — no key, no third-party service, instant. Educational estimates, not medical advice. Live, nothing stored. 3 compute endpoints.

api.oanor.com/sunscreen-api

Frequently asked questions

Quick answers about pricing, quotas, and integration.

How do I get an API key for Sample Size API?
Sign up for free at oanor.com, generate an API key from the developer dashboard, and call Sample Size API with the x-oanor-key header. No credit card needed for the free tier.
What's the rate limit for Sample Size API?
Free tier allows 1 request per second. Paid plans scale up to 50 requests per second on the Mega tier. Hard limits return HTTP 429 above the quota — no surprise overage charges.
How much does Sample Size API cost?
Sample Size API has a free tier with 100 calls / month. Paid plans start at €5.60 / month with higher quotas and faster rate limits.
Can I cancel my subscription anytime?
Yes. Plans are billed monthly and you can cancel anytime from your billing dashboard. No long-term contracts and no cancellation fee.
Is Sample Size API GDPR-compliant?
All requests to Sample Size API go through our EU-based gateway. Your upstream API key never leaves our server and no personal data is shared with the upstream provider beyond the request you send.

Pick an endpoint from the list on the left to see its details and try it.

Code snippets

Sign up to get an API key, then call any path under your slug.

curl https://api.oanor.com/samplesize-api/SOME_PATH \
  -H "x-oanor-key: oanor_test_..."
const res = await fetch("https://api.oanor.com/samplesize-api/SOME_PATH", {
  headers: { "x-oanor-key": "oanor_test_..." }
});
const data = await res.json();
$ch = curl_init("https://api.oanor.com/samplesize-api/SOME_PATH");
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_HTTPHEADER, ["x-oanor-key: oanor_test_..."]);
$response = curl_exec($ch);
import requests
r = requests.get(
    "https://api.oanor.com/samplesize-api/SOME_PATH",
    headers={"x-oanor-key": "oanor_test_..."},
)
print(r.json())

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