問3
頻出度★★★
投資会社であるA社が，それぞれの投資戦略を採る場合の利益は，表のように予想される。A社がマクシミン戦略を採り，かつ，市況が好転した場合の利益はどれか。マクシミン戦略とは，戦略ごとに予想される利益の最小値が最も大きくなるように戦略を採用する理論である。
| 市況が好転 | 市況が悪化 | |
|---|---|---|
| 投資戦略 a | 20 | −15 |
| 投資戦略 b | 5 | 0 |
令和8年度 ITパスポート試験 問3
ストラテジ系企業活動 › 業務分析・データ利活用
This question's explanation and your answers so far.
解説
問 3
Incorrectア
−15 is strategy a’s profit when the market worsens. Strategy a’s minimum profit is −15, which is smaller than strategy b’s 0, so it is not chosen under the maximin strategy. This is the mistake of taking the minimum value itself as the answer.
Incorrectイ
0 is the “minimum profit (when the market worsens)” of the adopted strategy b. This is the mistake of directly using the minimum value (the one used to make the maximin decision) as the answer, whereas the question asks for the profit when the market improves.
- ウ
正解 In the maximin strategy, you first find the “worst outcome (minimum profit)” for each strategy. For strategy a, the smaller of 20 and −15 is −15; for strategy b, the smaller of 5 and 0 is 0. Next, you choose the strategy whose minimum profit is the largest; since 0 > −15, strategy b is adopted. The question then asks for the profit “when the market improves,” so you read strategy b’s value when the market improves, which is 5. Therefore the correct answer is ウ, 5.
Incorrectエ
20 is strategy a’s profit when the market improves. This reflects jumping at the largest profit (a maximax-style approach), but strategy a’s minimum profit is −15, so it is not adopted under the maximin strategy.
ここがポイント
- Maximin strategy = compare the minimum profit of each strategy and choose the one whose minimum profit is the largest (a conservative decision that minimizes the loss in the worst case).
- Solve in two steps = ① select the strategy by comparing minimum profits (here, strategy b), then ② read the profit for the specified scenario (the market improves) from the table.
用語