# Outlier detector

> Compare IQR and z-score flags without automatically deleting records.

[Open tool](https://www.toolcabana.com/su/outlier-detector) · [Statistics and analysis](https://www.toolcabana.com/su/category/statistics-and-analysis)

Tool ID: outlier-detector. Requested language: su. Description language: en. Complete guide translation: no; untranslated sections use English.

## Overview (en)

The Outlier detector takes a list of numbers and flags possible outliers with either the IQR method or a z-score threshold, returning a table of each value's position, value and true or false flag. The multiplier or threshold can be set from 0.1 to 10, with 1.5 as the default. Values are only flagged; nothing is removed from your data.

## Supported tasks (en)

Compare IQR and z-score flags without automatically deleting records.

## Steps (en)

1. Paste the source into the input editor, or load the built-in example.
2. Set method, multiplier / z-score threshold.
3. Run outlier detector, review the output, then use the available copy or download controls.

## Settings

- Method (en; key: method; type: select): IQR [en], z-score [en]
- Multiplier / z-score threshold (en; key: threshold; type: number); minimum: 0.1; maximum: 10

## Limitations (en)

Local bounded calculations. Numeric inputs must be finite and within the visible ranges. Lists and tables have operation-specific limits. Models, estimates and supplied rates must be checked against your intended use.

## Example input

```text
1,2,3,4,5,6,100
```

## Privacy and connections (en)

This operation processes its source in your browser. Copy and download are explicit actions; source input is not saved in an account or history.

## Questions (en)

### How does the IQR outlier method work?

The detector finds the first and third quartiles, Q1 and Q3, and the interquartile range IQR = Q3 − Q1. A value is flagged when it is below Q1 − k × IQR or above Q3 + k × IQR, where k is the multiplier, 1.5 by default.

### How does the z-score method flag outliers?

Each value's z-score is (value − mean) / standard deviation, using the population standard deviation. A value is flagged when the absolute z-score is greater than your threshold. Common choices are 2 or 3; if every value is identical, nothing is flagged.

### Which outlier method should I use?

IQR is based on quartiles, so a single extreme value barely affects the fences, which suits skewed data. The z-score method uses the mean and standard deviation, which an extreme value can inflate and partially mask. Comparing both on the same list shows where they disagree.

### Where is my input processed?

This operation processes its source in your browser. Copy and download are explicit actions; source input is not saved in an account or history.

### What are the input limits?

Local bounded calculations. Numeric inputs must be finite and within the visible ranges. Lists and tables have operation-specific limits. Models, estimates and supplied rates must be checked against your intended use.

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