予測 and 想定: forecasts, planning assumptions, and expectations
Compare forecasts based on records with backup lighting prepared for an assumed blackout. Read 予測 and 想定 through future estimates, planning assumptions, and attendance beyond an original expectation.
予測 looks ahead from evidence
予測 (よそく) is used for a judgment about what lies ahead. 「過去の記録から来月の利用者数を予測した。」 means “We predicted next month's number of users based on past records.” The records provide the basis, while next month's user count is the prediction.
「山の天気を正確に予測するのは難しい。」 means “It is difficult to predict mountain weather accurately.” The difficulty concerns an accurate forecast. The first sentence reports making a prediction; this one describes forecasting difficulty. Neither fixes the actual weather or user count.
想定 supplies a planning situation or an original expectation
想定 (そうてい) can name a situation assumed for preparation. 「停電を想定して予備の明かりを用意した。」 means “We prepared backup lighting on the assumption of a power outage.” Preparing the lighting is the action reported; a blackout is the assumed situation.
「当初の想定を超える人数が会場に集まった。」 means “More people gathered at the venue than originally expected.” The original expectation supplies a reference for attendance. More people did gather, but neither the expected nor the actual count is specified.
Find what was forecast and what was assumed
Predicting next month's users looks forward using past records. Assuming a blackout supplies a situation to prepare for. The attendance sentence also uses 想定 for what was originally expected, so the word should not be limited to preparations alone.
予測した and 用意した report a prediction and a preparation respectively. They do not establish the eventual user count or an actual blackout. Identify the content of the forecast and the situation used for planning before drawing a conclusion about what happened.
What is forecast in the next-month user example, and what is assumed in the blackout preparation example?
Show the answer and why
The user count is a future estimate based on records. A blackout is a situation assumed so that lighting can be prepared. Preparing the lighting does not itself show that a blackout occurred.