Box plots from real statistics of Japan's municipalities
Choose a prefecture and a measure to draw a box plot and quartiles from the real values (population, numbers of elementary and junior high schools, pupils and students) of every municipality in it. Your municipality is marked so you can see where it sits, and you can put a second prefecture alongside to compare. No typing numbers, no spreadsheet. Made for teaching box plots in lower-secondary maths (ages 13–14).
Names are in Japanese only (the data set has no romanized names).
Choose a prefecture to draw a box plot from the values of all its municipalities.
Axis:
Values of all municipalities (largest first)
Questions for class
- Roughly what share of the municipalities fall inside the box (from the first to the third quartile)? Count them in the list of all values to check.
- Is your municipality on the larger or the smaller side within its prefecture? Add a prefecture to compare: how do the position and length of the box (the interquartile range) differ? If a box looks squashed, a municipality with a very large value is stretching the axis. Find it.
- Which municipalities have a particularly small or particularly large value for “elementary schools per 10,000 people”? Think about why: a small population, school closures and mergers, and so on.
The numbers of elementary and junior high schools, pupils and students include combined elementary and junior high schools (a Japanese school type, gimu kyoiku gakko, that runs grades 1 to 9 in one school): their pupils in grades 1–6 are added to elementary school pupils and those in grades 7–9 to junior high school students.
When the number you divide by is 0 (for example, students per junior high school in a village with no junior high school), the value is shown as “—” and left out of the chart and table. When the number being divided is 0 (for example, junior high schools per 10,000 people in that village), it is a real 0 and is on the chart. A village with one junior high school and no students (for example, 王滝村 in Nagano) has 0.0 students per junior high school.
Quartiles follow the Japanese lower-secondary textbook method: sort the values, split them at the median into a lower and an upper half (with an odd count the median goes in neither half), and take the median of each half. With an odd count this equals Excel's QUARTILE.EXC; it can differ from QUARTILE.INC (plain QUARTILE), and from QUARTILE.EXC when the count is even. Designated cities count as one municipality (not split into wards); Tokyo's special wards count one by one.
Source: processed from the National Statistics Center (NSTAC) “Standardized Statistical Data Set for Education, SSDSE-A-2026” (About SSDSE (NSTAC, Japanese))