als-statistics/docs/05-table/03-cronbach.md

A powerful and lightweight JavaScript library for descriptive statistics, regression, clustering, outlier detection, and noise analysis using a flexible table/column architecture.

## 📏 Cronbach's Alpha

Cronbach’s Alpha measures internal consistency — how closely related a set of numeric items are.

### 🔹 Use Cases
- Questionnaires and surveys
- Psychometric analysis
- Testing item reliability

### 🔹 Usage

```js
const table = Statistics.newTable({
  Q1: [4, 5, 3, 4, 5],
  Q2: [3, 4, 2, 3, 4],
  Q3: [5, 3, 4, 5, 2]
});

const alpha = table.cronbachAlpha;
console.log(alpha.alpha); // Example: 0.74
```

### 🔹 Item Deletion Diagnostics

```js
console.log(alpha.perColumn);
// { Q1: 0.65, Q2: 0.68, Q3: 0.71 }
```

### 🔹 Notes
- Requires 2+ numeric columns.
- If all responses are identical, `alpha = 0`.