First Quartile Calculator
Enter a dataset to compute Q1, alongside other quartiles and summary values. Choose inclusive or exclusive quartile definitions.
Q1 (first quartile): 15.0000
Median (Q2): 21.0000
Q3 (third quartile): 27.0000
Minimum: 12
Maximum: 30
Count: 7
How to Use This Calculator
- Enter the dataset values separated by spaces or commas.
- Select the quartile method (inclusive or exclusive) based on your preference.
- Review the computed quartiles and summary statistics.
- Use Q1 to understand the lower 25% of the data distribution.
Formula
Inclusive: Q1 = median of data at position (n + 1) / 4
Exclusive: Split data at median, take median of lower half
Interpolate when positions fall between indices
Full Description
Quartiles partition data into four equal segments. The first quartile marks the value below which 25% of observations fall. Different statistical packages adopt varying definitions (inclusive or exclusive), so the calculator provides both for clarity.
Frequently Asked Questions
Which quartile method should I use?
Inclusive (Tukey) aligns with many textbook definitions. Exclusive matches certain statistical software. Apply the method consistent with your analysis.
How are quartiles different from percentiles?
Quartiles are specific percentiles: Q1 is the 25th percentile, Q2 is the 50th, Q3 is the 75th.
Does dataset size matter?
Quartile calculations adjust for dataset length, using interpolation as needed. Larger samples yield more stable results.
Can I handle repeated values?
Yes. The calculator sorts the dataset and treats duplicates naturally within the quartile computation.