Skills - Data Interpretation, Charts, Maps, and Source Analysis
What is being measured
Whether you can read a statistic honestly: identify units and year, spot a broken axis, convert a scale bar into kilometres, calculate a time difference, and judge what a historical source can and cannot prove.
Rules that apply across questions
- Every graph answer needs three checks: unit (万人 vs 人, %, 億円), year, and whether the vertical axis starts at zero.
- 円グラフ and 帯グラフ show proportions, not absolute numbers; always ask what the total was.
- Scale: 1/25,000 means 1 cm on paper equals 250 m on the ground; 1/50,000 means 1 cm equals 500 m.
- Time zones: 15 degrees of longitude equals one hour; add when moving east, and subtract across the 日付変更線.
- Contour maps: closely spaced lines mean steep ground; a V pointing uphill marks a valley.
- Sources: distinguish 一次資料 from later commentary, and note the writer's position before trusting the content.
Worked example
It is 1 January, 9:00 a.m. in Japan (東経135度). What time is it at 東経15度? Japan is 135 ÷ 15 = 9 hours ahead of UTC; 15度 East is one hour ahead, so the difference is eight hours. 9:00 minus 8 hours gives 1 January, 1:00 a.m. A quick self-check: the place is west of Japan, so its clock must read earlier.
Traps that cost marks
Reading a 折れ線グラフ whose vertical axis starts at 80% as if the change were enormous; comparing 割合 across regions with different populations; multiplying by the scale denominator but forgetting to convert cm to m; and treating a later history textbook's summary as a primary source.