{
  "title": "Statistical test selection guide",
  "human_url": "https://happytails.ai/en/calculators/statistical-test-selection-guide/",
  "agent_url": "https://happytails.ai/agents/en/calculators/statistical-test-selection-guide/",
  "language": "en",
  "markdown_url": "https://happytails.ai/en/calculators/statistical-test-selection-guide.md",
  "content": "Statistical test selection guide\nAnswer a few questions about your question, outcome and groups to get a ranked list of suitable methods, the assumptions each one needs, and a link to the Happytails.ai tool that runs it.\nHow can we improve this tool?\nReport a problem or share an idea.\nPlease leave out private information. Your message and the tool name go to our team via PostHog.\nHow to use Statistical test selection guide\nChoose what you want to find out and the type of outcome.\nFor comparisons, give the number of groups, pairing, the smallest group size and what you know about normality and spread.\nRun the guide and read the recommended method and the alternatives.\nOpen the linked tool, or download the list.\nUseful next steps\nCorrelation comparison\nAgreement analysis\nSample size calculator\nHow suggestions are made\nFixed rules map your answers to methods. Comparisons of continuous outcomes suggest Welch's t test or Welch's ANOVA first; small groups with doubtful normality, ordinal outcomes and counts put rank tests first. Binary and category outcomes of independent groups suggest chi-square or Fisher's exact test. Paired yes/no data get McNemar's test for two measurements and Cochran's Q, run as the Friedman test on 0 and 1 codes, for three or more; one sample of yes/no outcomes gets the exact binomial test against a reference proportion. Paired category outcomes and one sample of categories are marked not suitable, because the Stuart-Maxwell, Bowker and goodness-of-fit tests they need are not available here. Other questions lead to regression, agreement, reliability, diagnostic accuracy, distribution, time series or meta-analysis tools.\nReading the list\nEach candidate is marked recommended, alternative or not suitable, with fixed sentences for assumptions you have not confirmed, such as equal variances for Student's t test. Every suggestion links to the Happytails.ai page that runs it; a method marked not suitable links back to this guide.\nLimits\nThe rules cover the methods in this catalogue only and cannot see your data or study design. They are a starting point to check with someone who knows the study, not a statistical review.",
  "content_format": "text/plain",
  "visibility": "public",
  "links": [
    {
      "name": "Correlation comparison",
      "url": "https://happytails.ai/en/calculators/correlation-comparison/"
    },
    {
      "name": "Agreement analysis",
      "url": "https://happytails.ai/en/calculators/agreement-analysis/"
    },
    {
      "name": "Sample size calculator",
      "url": "https://happytails.ai/en/calculators/sample-size-calculator/"
    }
  ],
  "tool": {
    "id": "statistical-test-selection-guide",
    "category": "calculators",
    "built": true,
    "requirements": "Runs locally in your browser; nothing is uploaded. Form answers only: question, outcome type, number of groups, pairing, the smallest group size (a whole number of at least 1), normality, equal spread and small expected counts. Downloads: a JSON report and a CSV list of candidates with their page paths.",
    "implementation": {
      "fields": [
        {
          "key": "question",
          "label": "Question",
          "value": "compare",
          "type": "select",
          "values": [
            "compare",
            "association",
            "predict",
            "agreement",
            "reliability",
            "diagnostic",
            "distribution",
            "time-series",
            "meta-analysis"
          ],
          "labels": {
            "compare": "Compare groups or conditions",
            "association": "Measure an association",
            "predict": "Predict an outcome",
            "agreement": "Check agreement between raters or methods",
            "reliability": "Check scale reliability",
            "diagnostic": "Evaluate a diagnostic or classification test",
            "distribution": "Check a distribution",
            "time-series": "Describe a time series",
            "meta-analysis": "Combine study results"
          }
        },
        {
          "key": "outcome",
          "label": "Outcome type",
          "value": "continuous",
          "type": "select",
          "values": [
            "continuous",
            "ordinal",
            "binary",
            "nominal",
            "count",
            "time-to-event"
          ],
          "labels": {
            "continuous": "Continuous measurement",
            "ordinal": "Ordered categories or ranks",
            "binary": "Yes or no",
            "nominal": "Unordered categories",
            "count": "Counts",
            "time-to-event": "Time until an event"
          }
        },
        {
          "key": "groups",
          "label": "Number of groups",
          "value": "two",
          "type": "select",
          "values": [
            "two",
            "one",
            "three-plus"
          ],
          "labels": {
            "two": "Two",
            "one": "One sample against a reference",
            "three-plus": "Three or more"
          },
          "showWhen": {
            "question": [
              "compare"
            ]
          }
        },
        {
          "key": "paired",
          "label": "Same subjects measured more than once (paired or repeated)",
          "value": false,
          "type": "checkbox"
        },
        {
          "key": "minGroupSize",
          "label": "Smallest group size",
          "value": "30",
          "type": "text",
          "maxLength": 20,
          "help": "Whole number of at least 1.",
          "showWhen": {
            "question": [
              "compare"
            ]
          }
        },
        {
          "key": "normality",
          "label": "Does the outcome look roughly normal?",
          "value": "unknown",
          "type": "select",
          "values": [
            "unknown",
            "plausible",
            "doubtful"
          ],
          "labels": {
            "unknown": "Not checked",
            "plausible": "Plausible",
            "doubtful": "Doubtful (skewed or outliers)"
          }
        },
        {
          "key": "equalVariance",
          "label": "Similar spread in every group?",
          "value": "unknown",
          "type": "select",
          "values": [
            "unknown",
            "yes",
            "no"
          ],
          "labels": {
            "unknown": "Not checked",
            "yes": "Yes",
            "no": "No"
          },
          "showWhen": {
            "question": [
              "compare"
            ]
          }
        },
        {
          "key": "smallCounts",
          "label": "Some expected counts are below 5",
          "value": false,
          "type": "checkbox"
        }
      ],
      "registrationFamily": "statistical-comparison-tests",
      "input": false,
      "note": "Runs on your device. Suggestions follow fixed rules and link to the matching Happytails.ai tool.",
      "experience": {
        "automatic": false,
        "single": false,
        "inputMaxLength": 1000000,
        "inputMode": "text",
        "label": "Study questions",
        "placeholder": "Answer the questions in the form fields",
        "help": "Choose the question and outcome first; group questions apply to comparisons. Up to 1,000,000 characters. Review the settings before running.",
        "action": null
      },
      "mode": "explicit",
      "interactive": false
    },
    "execution": "Browser interface",
    "api": null,
    "browser_agent": {
      "supported": true,
      "name": "run_current_tool",
      "discovery": "WebMCP on the human page in a supporting browser",
      "verification": "See audit/API-AUDIT.md; availability is not verification"
    }
  },
  "markdown": "# Statistical test selection guide\n\n- Human page: https://happytails.ai/en/calculators/statistical-test-selection-guide/\n- Markdown: https://happytails.ai/en/calculators/statistical-test-selection-guide.md\n- Structured JSON: https://happytails.ai/agents/en/calculators/statistical-test-selection-guide/index.json\n- Visibility: public\n\n## Tool capabilities\n\n| Property | Value |\n| --- | --- |\n| Tool ID | `statistical-test-selection-guide` |\n| Category | calculators |\n| Implementation | Registered implementation. Registration alone is not a production-quality guarantee. |\n| Browser execution | Use the visible action or interactive controls. |\n| Browser processing | Browser; see tool notes for network behavior. |\n| HTTP API | Not callable through HTTP. |\n| Browser-agent interface | run_current_tool |\n\n### Implementation notes\n\nRuns on your device. Suggestions follow fixed rules and link to the matching Happytails.ai tool.\n\n### Inputs and settings\n\nNo free-text input is required. Use the file inputs and/or settings below.\n\n| Setting | Meaning | Control type | Default | Constraints |\n| --- | --- | --- | --- | --- |\n| `question` | Question | select | \"compare\" | Allowed: compare, association, predict, agreement, reliability, diagnostic, distribution, time-series, meta-analysis |\n| `outcome` | Outcome type | select | \"continuous\" | Allowed: continuous, ordinal, binary, nominal, count, time-to-event |\n| `groups` | Number of groups | select | \"two\" | Allowed: two, one, three-plus |\n| `paired` | Same subjects measured more than once (paired or repeated) | checkbox | false |  |\n| `minGroupSize` | Smallest group size | text | \"30\" |  |\n| `normality` | Does the outcome look roughly normal? | select | \"unknown\" | Allowed: unknown, plausible, doubtful |\n| `equalVariance` | Similar spread in every group? | select | \"unknown\" | Allowed: unknown, yes, no |\n| `smallCounts` | Some expected counts are below 5 | checkbox | false |  |\n\n### Browser-agent workflow\n\n1. Open the human page in a browser that supports WebMCP.\n2. Discover the interface exposed by that page; use its actual schema.\n3. Select files on the page first when the tool requires files.\n4. Call `run_current_tool` with valid input and settings.\n5. Inspect the returned result or error and the displayed output. Retrieve files from the displayed download links.\n\nCalls do not automatically copy or download results. Browser permissions still apply. Interface availability alone is not proof of successful execution.\n\n### Planning specification\n\nRuns locally in your browser; nothing is uploaded. Form answers only: question, outcome type, number of groups, pairing, the smallest group size (a whole number of at least 1), normality, equal spread and small expected counts. Downloads: a JSON report and a CSV list of candidates with their page paths.\n\nThis describes intended requirements. Use the implementation notes, interface schema and observed output to determine current support.\n\n### Complete machine-readable capability record\n\n```json\n{\n  \"id\": \"statistical-test-selection-guide\",\n  \"category\": \"calculators\",\n  \"built\": true,\n  \"requirements\": \"Runs locally in your browser; nothing is uploaded. Form answers only: question, outcome type, number of groups, pairing, the smallest group size (a whole number of at least 1), normality, equal spread and small expected counts. Downloads: a JSON report and a CSV list of candidates with their page paths.\",\n  \"implementation\": {\n    \"fields\": [\n      {\n        \"key\": \"question\",\n        \"label\": \"Question\",\n        \"value\": \"compare\",\n        \"type\": \"select\",\n        \"values\": [\n          \"compare\",\n          \"association\",\n          \"predict\",\n          \"agreement\",\n          \"reliability\",\n          \"diagnostic\",\n          \"distribution\",\n          \"time-series\",\n          \"meta-analysis\"\n        ],\n        \"labels\": {\n          \"compare\": \"Compare groups or conditions\",\n          \"association\": \"Measure an association\",\n          \"predict\": \"Predict an outcome\",\n          \"agreement\": \"Check agreement between raters or methods\",\n          \"reliability\": \"Check scale reliability\",\n          \"diagnostic\": \"Evaluate a diagnostic or classification test\",\n          \"distribution\": \"Check a distribution\",\n          \"time-series\": \"Describe a time series\",\n          \"meta-analysis\": \"Combine study results\"\n        }\n      },\n      {\n        \"key\": \"outcome\",\n        \"label\": \"Outcome type\",\n        \"value\": \"continuous\",\n        \"type\": \"select\",\n        \"values\": [\n          \"continuous\",\n          \"ordinal\",\n          \"binary\",\n          \"nominal\",\n          \"count\",\n          \"time-to-event\"\n        ],\n        \"labels\": {\n          \"continuous\": \"Continuous measurement\",\n          \"ordinal\": \"Ordered categories or ranks\",\n          \"binary\": \"Yes or no\",\n          \"nominal\": \"Unordered categories\",\n          \"count\": \"Counts\",\n          \"time-to-event\": \"Time until an event\"\n        }\n      },\n      {\n        \"key\": \"groups\",\n        \"label\": \"Number of groups\",\n        \"value\": \"two\",\n        \"type\": \"select\",\n        \"values\": [\n          \"two\",\n          \"one\",\n          \"three-plus\"\n        ],\n        \"labels\": {\n          \"two\": \"Two\",\n          \"one\": \"One sample against a reference\",\n          \"three-plus\": \"Three or more\"\n        },\n        \"showWhen\": {\n          \"question\": [\n            \"compare\"\n          ]\n        }\n      },\n      {\n        \"key\": \"paired\",\n        \"label\": \"Same subjects measured more than once (paired or repeated)\",\n        \"value\": false,\n        \"type\": \"checkbox\"\n      },\n      {\n        \"key\": \"minGroupSize\",\n        \"label\": \"Smallest group size\",\n        \"value\": \"30\",\n        \"type\": \"text\",\n        \"maxLength\": 20,\n        \"help\": \"Whole number of at least 1.\",\n        \"showWhen\": {\n          \"question\": [\n            \"compare\"\n          ]\n        }\n      },\n      {\n        \"key\": \"normality\",\n        \"label\": \"Does the outcome look roughly normal?\",\n        \"value\": \"unknown\",\n        \"type\": \"select\",\n        \"values\": [\n          \"unknown\",\n          \"plausible\",\n          \"doubtful\"\n        ],\n        \"labels\": {\n          \"unknown\": \"Not checked\",\n          \"plausible\": \"Plausible\",\n          \"doubtful\": \"Doubtful (skewed or outliers)\"\n        }\n      },\n      {\n        \"key\": \"equalVariance\",\n        \"label\": \"Similar spread in every group?\",\n        \"value\": \"unknown\",\n        \"type\": \"select\",\n        \"values\": [\n          \"unknown\",\n          \"yes\",\n          \"no\"\n        ],\n        \"labels\": {\n          \"unknown\": \"Not checked\",\n          \"yes\": \"Yes\",\n          \"no\": \"No\"\n        },\n        \"showWhen\": {\n          \"question\": [\n            \"compare\"\n          ]\n        }\n      },\n      {\n        \"key\": \"smallCounts\",\n        \"label\": \"Some expected counts are below 5\",\n        \"value\": false,\n        \"type\": \"checkbox\"\n      }\n    ],\n    \"registrationFamily\": \"statistical-comparison-tests\",\n    \"input\": false,\n    \"note\": \"Runs on your device. Suggestions follow fixed rules and link to the matching Happytails.ai tool.\",\n    \"experience\": {\n      \"automatic\": false,\n      \"single\": false,\n      \"inputMaxLength\": 1000000,\n      \"inputMode\": \"text\",\n      \"label\": \"Study questions\",\n      \"placeholder\": \"Answer the questions in the form fields\",\n      \"help\": \"Choose the question and outcome first; group questions apply to comparisons. Up to 1,000,000 characters. Review the settings before running.\",\n      \"action\": null\n    },\n    \"mode\": \"explicit\",\n    \"interactive\": false\n  },\n  \"execution\": \"Browser interface\",\n  \"api\": null,\n  \"browser_agent\": {\n    \"supported\": true,\n    \"name\": \"run_current_tool\",\n    \"discovery\": \"WebMCP on the human page in a supporting browser\",\n    \"verification\": \"See audit/API-AUDIT.md; availability is not verification\"\n  }\n}\n```\n\n## Page guide\n\nAnswer a few questions about your question, outcome and groups to get a ranked list of suitable methods, the assumptions each one needs, and a link to the Happytails.ai tool that runs it.\n\nHow can we improve this tool?\n\nReport a problem or share an idea.\n\nPlease leave out private information. Your message and the tool name go to our team via PostHog.\n\n### How to use Statistical test selection guide\n\n1. Choose what you want to find out and the type of outcome.\n2. For comparisons, give the number of groups, pairing, the smallest group size and what you know about normality and spread.\n3. Run the guide and read the recommended method and the alternatives.\n4. Open the linked tool, or download the list.\n\n## Useful next steps\n\n- [Correlation comparison](https://happytails.ai/en/calculators/correlation-comparison/) ([Markdown](https://happytails.ai/en/calculators/correlation-comparison.md))\n\n- [Agreement analysis](https://happytails.ai/en/calculators/agreement-analysis/) ([Markdown](https://happytails.ai/en/calculators/agreement-analysis.md))\n\n- [Sample size calculator](https://happytails.ai/en/calculators/sample-size-calculator/) ([Markdown](https://happytails.ai/en/calculators/sample-size-calculator.md))\n\n## How suggestions are made\n\nFixed rules map your answers to methods. Comparisons of continuous outcomes suggest Welch's t test or Welch's ANOVA first; small groups with doubtful normality, ordinal outcomes and counts put rank tests first. Binary and category outcomes of independent groups suggest chi-square or Fisher's exact test. Paired yes/no data get McNemar's test for two measurements and Cochran's Q, run as the Friedman test on 0 and 1 codes, for three or more; one sample of yes/no outcomes gets the exact binomial test against a reference proportion. Paired category outcomes and one sample of categories are marked not suitable, because the Stuart-Maxwell, Bowker and goodness-of-fit tests they need are not available here. Other questions lead to regression, agreement, reliability, diagnostic accuracy, distribution, time series or meta-analysis tools.\n\n### Reading the list\n\nEach candidate is marked recommended, alternative or not suitable, with fixed sentences for assumptions you have not confirmed, such as equal variances for Student's t test. Every suggestion links to the Happytails.ai page that runs it; a method marked not suitable links back to this guide.\n\n### Limits\n\nThe rules cover the methods in this catalogue only and cannot see your data or study design. They are a starting point to check with someone who knows the study, not a statistical review.\n"
}