Comprehensive Calculator Guide
This calculator finds the lower quartile Q1, median Q2, upper quartile Q3 and interquartile range of any data, by the median-of-halves method used in schools, with the steps. For 6, 7, 15, 36, 39, 40, 41, 42, 43, 47, 49 the quartiles are 15, 40 and 43, IQR 28.
Quartiles
Sort, find the median, split into halves (leaving the median out for odd counts), and take each half’s median. A quarter of the data lies below Q1 and a quarter above Q3. Excel’s QUARTILE.INC interpolates and can differ.
How to Use
- Enter the data.
- At least two values.
- Press “Calculate” to see Q1, Q2, Q3 and the IQR.
Formula Used
Q1, Q3 = medians of the lower and upper halves | IQR = Q3 − Q1
Practical Examples
- Example 1
- 15, 40, 43; IQR 28.
- Example 2
- Marks: 77.5, 87.5, 90; IQR 12.5.
Important Tips
- Sort first.
- Check your book’s method.
- Use the IQR for outliers.
Common Mistakes to Avoid
- Unsorted data.
- Including the median in both halves.
- Confusing Q1 with P10.
Frequently Asked Questions
- What is Q1?
- The median of the lower half.
- IQR?
- Q3 − Q1.
- Why does Excel differ?
- A different method.