1. What Is SDI?

SDI (Standard Deviation Index) is a measure of variability that compares the spread of data to the mean value. It's commonly used in laboratory quality control and process variability analysis.

2. How Does the Calculator Work?

The calculator uses the SDI equation:

Where:

• \( max \) — Maximum value in the dataset
• \( min \) — Minimum value in the dataset
• \( average \) — Mean value of the dataset

Explanation: The equation measures the spread of data relative to the mean, expressed as a percentage.

3. Importance of SDI Calculation

Details: SDI helps assess data consistency and variability. Lower SDI values indicate more consistent data, while higher values suggest greater variability.

4. Using the Calculator

Tips: Enter the maximum, minimum, and average values from your dataset. The average must be greater than zero for valid calculation.

5. Frequently Asked Questions (FAQ)

Q1: What is a good SDI value?
A: Generally, SDI below 10% indicates good consistency, while above 20% suggests significant variability.

Q2: How is SDI different from standard deviation?
A: SDI expresses variability as a percentage of the mean, making it easier to compare across different scales.

Q3: When should I use SDI?
A: SDI is particularly useful in quality control, laboratory testing, and any situation where relative variability matters.

Q4: Can SDI be negative?
A: No, since it's based on the range (max-min) divided by the average, SDI is always positive.

Q5: What if my average is zero?
A: The calculation is undefined when average is zero. Ensure you have valid, non-zero data.