Cohen's d effect size API

Compute Cohen's d effect size d=(x̄1−x̄2)/s_pooled (pooled sd from both samples) from raw samples or summary stats, with the standard small/medium/large rating. Auditable: returns pooled sd and means. Answers 'effect size between two groups','Cohen d for these means','how big is the difference'.

Price$0.01per request

MethodPOST

Route/v1/calc/stat-cohens-d

StatusLive

MIME typeapplication/json

Rate limit120/minute

CacheNo cache

calcstatisticseffect-sizecohens-dpooled-sdcomparisonmagnitudegroups

API URLhttps://x402.hexl.dev/v1/calc/stat-cohens-d

Integration docs

Example request

{
  "mean1": 110,
  "mean2": 100,
  "sd1": 15,
  "sd2": 15,
  "n1": 30,
  "n2": 30
}

Example response

{
  "cohensD": 0.666667,
  "pooledSd": 15,
  "mean1": 110,
  "mean2": 100,
  "meanDifference": 10,
  "rating": "medium",
  "interpretation": "Cohen's d = 0.6667 (medium effect); 0.667 pooled SDs apart."
}

Input schema

{
  "type": "object",
  "required": [],
  "properties": {
    "sample1": {
      "type": "array",
      "items": {
        "type": "number"
      }
    },
    "sample2": {
      "type": "array",
      "items": {
        "type": "number"
      }
    },
    "mean1": {
      "type": "number",
      "examples": [
        110
      ]
    },
    "mean2": {
      "type": "number",
      "examples": [
        100
      ]
    },
    "sd1": {
      "type": "number",
      "examples": [
        15
      ]
    },
    "sd2": {
      "type": "number",
      "examples": [
        15
      ]
    },
    "n1": {
      "type": "number",
      "examples": [
        30
      ]
    },
    "n2": {
      "type": "number",
      "examples": [
        30
      ]
    }
  }
}

Output schema

{
  "type": "object",
  "additionalProperties": true
}