Whisker chart meaning in statistics
A “whisker chart on Google Sheets” is a box-and-whisker plot (often called a box plot). It summarizes a quantitative dataset using the five-number summary: \[ \text{min},\ Q_1,\ \text{median},\ Q_3,\ \text{max}. \]
The box spans the interquartile range \(IQR\), where: \[ IQR = Q_3 - Q_1. \]
What the parts represent
| Part | Statistic | Interpretation |
|---|---|---|
| Left edge of box | \(Q_1\) (25th percentile) | About 25% of values lie at or below this point. |
| Line inside box | Median (50th percentile) | Half the data are below, half above. |
| Right edge of box | \(Q_3\) (75th percentile) | About 75% of values lie at or below this point. |
| Whiskers | Spread outside the box | Depending on chart settings/software, whiskers may extend to min/max or to the most extreme non-outliers under the \(1.5\cdot IQR\) rule. |
| Outliers (if shown) | Unusually far values | Often defined by thresholds \[ L = Q_1 - 1.5\cdot IQR,\quad U = Q_3 + 1.5\cdot IQR. \] |
How to make a whisker chart on Google Sheets
Google Sheets interfaces vary by version and account features. Two reliable pathways are common.
Method A: Built-in Box and whisker chart (if available)
- Place the raw data in a single column (example: values in column A, rows 2 to 101).
- Select the range containing the data.
- Use Insert → Chart.
- In the Chart editor, choose chart type Box and whisker (or Box plot).
- Confirm that the dataset is treated as a numeric series; adjust labels/legend only if needed.
Method B: Candlestick workaround using the five-number summary
A candlestick chart can be driven by \(\text{min}, Q_1, Q_3, \text{max}\) to mimic a box-and-whisker plot shape. This is useful when a dedicated box plot type is not offered.
- Keep raw data in one column (example range: A2:A101).
- Compute the summary statistics in separate cells (one row), for example:
- Minimum: MIN(A2:A101)
- Lower quartile: QUARTILE(A2:A101, 1)
- Upper quartile: QUARTILE(A2:A101, 3)
- Maximum: MAX(A2:A101)
- Select the cells containing the label plus the four values arranged as low / open / close / high (min / \(Q_1\) / \(Q_3\) / max).
- Use Insert → Chart and choose chart type Candlestick.
- Optional: compute the median with MEDIAN(A2:A101) and annotate it separately (for interpretation), since some candlestick renderings do not display the median line by default.
Worked example: interpreting a whisker chart
Suppose a dataset has five-number summary: \[ \text{min}=10,\quad Q_1=14,\quad \text{median}=18,\quad Q_3=21,\quad \text{max}=25. \] Then \[ IQR = 21 - 14 = 7, \quad L = 14 - 1.5\cdot 7 = 3.5, \quad U = 21 + 1.5\cdot 7 = 31.5. \] Values below \(3.5\) or above \(31.5\) would be flagged as outliers under the \(1.5\cdot IQR\) rule.
- The middle 50% of the data lie between 14 and 21.
- The median at 18 indicates the central location.
- Comparing whisker lengths helps judge skew: longer right whisker suggests right-skew; longer left suggests left-skew (when whiskers represent comparable rules).
Visualization: box-and-whisker anatomy
Common checks for correctness
- Raw data should be numeric (no mixed text) to avoid chart misclassification.
- Quartiles should satisfy \(\text{min}\le Q_1 \le \text{median}\le Q_3 \le \text{max}\).
- Interpretation should mention both center (median) and spread (\(IQR\) and whiskers), not only the extremes.