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A box plot (box-and-whisker plot) visualises the distribution of data using five statistics: minimum, Q1, median, Q3, and maximum. Outliers are shown as individual points beyond 1.5×IQR from the quartiles.
Wzór
Q1 = 25th percentile, Q2 (median) = 50th, Q3 = 75th; IQR = Q3 − Q1
- Min
- minimum value
- Q1
- first quartile (25th percentile)
- Q2
- median (50th percentile)
- Q3
- third quartile (75th percentile)
- Max
- maximum value
- IQR
- interquartile range — Q3 − Q1
Przewodnik krok po kroku
- 1Q2 (median): middle value of sorted data
- 2Q1: median of lower half
- 3Q3: median of upper half
- 4IQR = Q3 − Q1; outlier threshold = 1.5×IQR
Rozwiązane przykłady
Wejście
Data: 2,4,5,7,8,9,11,13
Wynik
Min=2, Q1=4.5, Med=7.5, Q3=10, Max=13
Wejście
IQR = 5.5, outlier threshold = 8.25 from quartiles
Wynik
Any value < −3.75 or > 18.25 is an outlier
Często zadawane pytania
What is a boxplot used for?
Boxplots visualize the distribution, spread, and outliers of data at a glance.
How are outliers determined in a boxplot?
Points beyond 1.5×IQR from Q1 or Q3 are typically marked as outliers.
Is the median always at the center of the box?
No, the line inside the box shows the median's position relative to Q1 and Q3, reflecting data skewness.
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