first quartile: meaning, definition, pronunciation and examples
C1Technical / Academic
Quick answer
What does “first quartile” mean?
The value below which 25% of the data in a dataset falls.
Audio
Pronunciation
Definition
Meaning and Definition
The value below which 25% of the data in a dataset falls; the 25th percentile.
A statistical measure used in descriptive statistics to divide a ranked dataset into four equal parts. The first quartile (Q1) marks the boundary between the lowest 25% of data points and the rest. It is a key measure of dispersion and non-central tendency, often used alongside the median and third quartile in box plots.
Dialectal Variation
British vs American Usage
Differences
No significant differences in meaning or usage between British and American English. The term is standardised in international academic and technical contexts.
Connotations
Purely technical, neutral. No regional connotations.
Frequency
Equal frequency in technical registers in both varieties.
Grammar
How to Use “first quartile” in a Sentence
The first quartile of [DATASET] is [VALUE].[VALUE] represents the first quartile.25% of [DATA] falls below the first quartile.Vocabulary
Collocations
Examples
Examples of “first quartile” in a Sentence
verb
British English
- [Not applicable. It is a noun phrase.]
American English
- [Not applicable. It is a noun phrase.]
adverb
British English
- [Not applicable.]
American English
- [Not applicable.]
adjective
British English
- [Rarely used adjectivally. Can be pre-modifying as in 'first-quartile households'.]
American English
- [Rarely used adjectivally. Can be pre-modifying as in 'first-quartile performance'.]
Usage
Meaning in Context
Business
Used in financial analysis, market research reports, and salary surveys to describe distribution (e.g., 'Salaries in the first quartile are below £30,000').
Academic
Core term in statistics, economics, social science, and STEM research papers for data description and box plot construction.
Everyday
Extremely rare. Might appear in news articles about income distribution, test scores, or health data.
Technical
Primary context. Used in data science, statistics software output, and scientific reporting.
Vocabulary
Synonyms of “first quartile”
Strong
Neutral
Weak
Vocabulary
Antonyms of “first quartile”
Watch out
Common Mistakes When Using “first quartile”
- Using 'first quartile' to mean 'top 25%' (that is the fourth quartile).
- Confusing it with the median (which is the second quartile).
- Saying 'in the first quartile' to mean a high rank (it actually indicates a low rank within the dataset).
FAQ
Frequently Asked Questions
Yes, they are exactly equivalent terms. The first quartile is the 25th percentile.
You order the data from smallest to largest and find the value at the 25th percentile. For a dataset with n values, the position is often calculated as (n+1)/4. Different methods (like Tukey's or Mendenhall's) may give slightly different results for certain datasets.
A 'quarter' refers to one of four equal groups of data (e.g., 'the bottom quarter'). A 'quartile' is a specific value that marks the boundary between those quarters (e.g., 'the first quartile is the cutoff point for the bottom quarter').
Typically, no. Quartiles require data that can be ranked or ordered numerically. They are not meaningful for purely categorical data (like colours or brands) unless those categories can be assigned an ordinal rank.
The value below which 25% of the data in a dataset falls.
First quartile is usually technical / academic in register.
First quartile: in British English it is pronounced /ˌfɜːst ˈkwɔː.taɪl/, and in American English it is pronounced /ˌfɜːrst ˈkwɔːr.taɪl/. Tap the audio buttons above to hear it.
Phrases
Idioms & Phrases
- “[No idioms. Purely technical term.]”
Learning
Memory Aids
Mnemonic
Think of 'quart' like 'quarter'. The FIRST quartile cuts off the FIRST quarter (25%) of the data.
Conceptual Metaphor
DIVISION / CUTOFF POINT. Data is imagined as a physical object (like a rod) that is cut into four pieces; the first cut creates the first quartile.
Practice
Quiz
If a student's score is at the first quartile (Q1) of the class, which statement is true?