---
title: "Anscombe's quartet"
styles: [scientific]
---

[Back to the chart gallery](https://richview.ai/docs/charts)

In 1973 F. J. Anscombe published four datasets with almost identical summaries and sharply different shapes. Plotting each set shows what a mean, variance or fitted equation can conceal.

```chart
{
  "annotations": [
    {
      "at": {
        "x": 8,
        "y": 13
      },
      "kind": "text",
      "text": "y = 3.00 + 0.500x"
    }
  ],
  "axes": {
    "x": {
      "label": "x"
    },
    "y": {
      "label": "y"
    }
  },
  "data": {
    "csv": "gallery/same-numbers/data/anscombe.csv"
  },
  "encoding": {
    "facet": "set",
    "x": "x",
    "y": "y"
  },
  "title": "A summary cannot show you the shape",
  "type": "scatter"
}
```

## Almost the same summary


The published observations are rounded, so the fitted values differ slightly. The means and x variance agree at the precision below; the small differences in y variance and correlation remain visible. Each rounded fitted relationship is y = 3.00 + 0.500x. The annotation repeats that shared rounded fit in each panel; it is not an extra set of observations.

| Statistic | Set I | Set II | Set III | Set IV |
| --- | --- | --- | --- | --- |
| Mean x | 9.00 | 9.00 | 9.00 | 9.00 |
| Sample variance x | 11.0 | 11.0 | 11.0 | 11.0 |
| Mean y | 7.50 | 7.50 | 7.50 | 7.50 |
| Sample variance y | 4.13 | 4.13 | 4.12 | 4.12 |
| Correlation r | 0.816 | 0.816 | 0.816 | 0.817 |


## Source

````rmd
---
title: "Anscombe's quartet"
styles: [scientific]
---

```chart
{
  "annotations": [
    {
      "at": {
        "x": 8,
        "y": 13
      },
      "kind": "text",
      "text": "y = 3.00 + 0.500x"
    }
  ],
  "axes": {
    "x": {
      "label": "x"
    },
    "y": {
      "label": "y"
    }
  },
  "data": {
    "csv": "data.csv"
  },
  "encoding": {
    "facet": "set",
    "x": "x",
    "y": "y"
  },
  "title": "A summary cannot show you the shape",
  "type": "scatter"
}
```

````

## Data and credits

[Complete report and provenance](https://richview.ai/docs/gallery/same-numbers/) · [Rich Markdown source](https://richview.ai/examples/charts/anscombe/report.rmd) · [CSV observations](https://richview.ai/docs/gallery/same-numbers/data/anscombe.csv).