📚 Year 7 CAIE Economics: Case Study Practice Drill | 七年级CAIE经济学：案例分析实战演练
Case study practice is one of the most effective ways to master the basics of economics. In this article, you will work through realistic examples that show how scarcity, choice, and opportunity cost shape everyday decisions. By analysing two step-by-step scenarios, you will gain confidence in applying economic reasoning – exactly what CAIE Year 7 Economics expects.
案例分析练习是掌握经济学基础最有效的方法之一。在本文中，你将通过真实情境的例子，看到稀缺性、选择和机会成本如何影响日常决策。通过逐步分析两个案例，你将建立应用经济推理的信心，这正是 CAIE 七年级经济学所要求的能力。
1. What is a Case Study in Economics? | 什么是经济学案例分析？
A case study is a description of a real or made-up situation that requires you to think like an economist. You are given information about people’s choices, resources, and constraints, and you must identify the economic problem and suggest a justified solution.
案例分析是对真实或虚构情境的描述，要求你像经济学家一样思考。你会得到关于人们选择、资源和限制的信息，必须识别经济问题并提出有依据的解决方案。
Case studies help you move beyond memorising definitions. They train you to spot scarcity, weigh trade-offs, and calculate opportunity cost in context – skills that will be tested in your exams.
案例分析帮助你超越死记硬背定义。它训练你在具体情境中发现稀缺性、权衡取舍并计算机会成本，这些技能会在考试中考查。
2. Core Economic Principles for Year 7 | 七年级核心经济学原理
Before you dive into a case, review these fundamental concepts. Scarcity means that resources are limited while wants are unlimited, so people must make choices. Every choice involves an opportunity cost – the value of the next best alternative forgone.
在深入案例之前，先复习这些基本概念。稀缺性意味着资源有限而欲望无限，因此人们必须做出选择。每一个选择都涉及机会成本——放弃的下一个最佳选择的价值。
Demand is the quantity of a good that consumers are willing and able to buy at different prices. Supply is the quantity that producers are willing to offer. Where demand and supply meet determines the market price. Understanding these building blocks will help you unpack any case study.
需求是消费者在不同价格下愿意并能够购买的商品数量。供给是生产者愿意提供的数量。需求与供给的相交决定了市场价格。理解这些基石有助于你剖析任何案例分析。
3. Step-by-Step Guide to Analysing a Case | 分析案例的分步指南
Step 1: Read the scenario twice. Highlight any numbers, names, and economic keywords such as ‘limited time’, ‘cost’, or ‘change in price’.
第一步：把情境读两遍。标出所有数字、人物名称和经济学关键词，例如“时间有限”、“成本”或“价格变化”。
Step 2: Identify the economic problem. Ask yourself: where is scarcity? What choices must be made? What are the trade-offs?
第二步：识别经济问题。问自己：哪里存在稀缺性？必须做出哪些选择？有什么权衡取舍？
Step 3: Define relevant concepts. Write a quick definition of opportunity cost, demand, supply, or any other term that fits the case.
第三步：定义相关概念。快速写出机会成本、需求、供给或其他适用于该案例的术语的定义。
Step 4: Apply the concepts. Use the numbers and facts from the case to calculate opportunity cost or explain why demand changed.
第四步：应用概念。使用案例中的数字和事实计算机会成本，或解释需求为何改变。
Step 5: Evaluate alternatives and conclude. Compare options, note any assumptions, and give a final recommendation supported by economic reasoning.
第五步：评估替代方案并得出结论。比较选项，注明任何假设，并给出有经济推理支持的最终建议。
4. Case 1: The Lemonade Stand Decision | 案例一：柠檬水小摊的决策
Sam has two weeks of summer holiday. He is considering three mutually exclusive plans. Option A: open a lemonade stand near the community pool. Ingredients and cups would cost $30, and he expects to earn $100 in total revenue if the weather stays sunny, leaving a net money gain of $70. Option B: help his neighbour with gardening for a fixed payment of $60. Option C: attend a free coding camp that offers no money but would teach him programming skills he personally values at $100. Sam can only pick one because his time is scarce.
萨姆有两周的暑假。他正在考虑三个互相排斥的计划。选项 A：在社区游泳池附近开设一个柠檬水小摊。原料和杯子将花费 30 美元，如果天气晴朗，他预计总收入为 100 美元，净货币收益为 70 美元。选项 B：为邻居整理花园，获得固定的 60 美元报酬。选项 C：参加一个免费的编程营，不带来金钱收入，但会教他编程技能，他个人认为这些技能价值 100 美元。萨姆只能选择一个，因为他的时间是稀缺的。
5. Identifying Scarcity and Choice | 识别稀缺性与选择
Sam faces a clear example of scarcity. He has only two weeks of holiday – a fixed time resource – but three competing uses for it. Scarcity forces him to make a choice because he cannot do all three activities at once.
萨姆面临一个明显的稀缺性例子。他只有两周假期——固定的时间资源——却有三个互相竞争的用途。稀缺性迫使他必须做出选择，因为他无法同时进行所有三项活动。
The economic problem here is: how should Sam allocate his scarce time to maximise his overall benefit, considering both money and personal satisfaction?
这里的经济问题是：萨姆应该如何分配他的稀缺时间，以最大化他的总体收益，既要考虑金钱，也要考虑个人满足感？
6. Calculating and Applying Opportunity Cost | 计算并应用机会成本
Opportunity cost is the value of the next best alternative that you give up when a choice is made. To find the opportunity cost of opening a lemonade stand, we must identify the best alternative Sam would have chosen otherwise.
机会成本是在做出选择时放弃的下一个最佳选择的价值。要找出开设柠檬水摊的机会成本，我们必须确定萨姆原本会选的最佳替代方案。
Let us assign a total benefit (money + personal valuation) to each option:
让我们为每个选项分配一个总收益（金钱 + 个人估价）：
| Option | Total Benefit |
|---|---|
| Lemonade stand | $70 |
| Gardening work | $60 |
| Coding camp | $100 |
If Sam chooses the lemonade stand, the next best option given up is the coding camp, which he values at $100. Therefore the opportunity cost is $100, not the $30 spent on ingredients. The lemonade stand’s net gain ($70) is less than the opportunity cost, so economically Sam would be better off attending the coding camp.
如果萨姆选择了柠檬水摊，放弃的下一个最佳选项是编程营，他对其估价为 100 美元。因此机会成本是 100 美元，而不是购买原料的 30 美元。柠檬水摊的净收益（70 美元）低于机会成本，因此从经济学角度看，萨姆参加编程营会更好。
7. Demand Factors at the Lemonade Stand | 柠檬水摊的需求因素
The demand for Sam’s lemonade depends on several factors. Hot weather increases the desire for a cold drink, shifting the demand curve to the right. The location near a busy swimming pool means many potential customers walk past. However, if a nearby shop sells bottled juice at a lower price, some customers will switch to that substitute, reducing the demand for lemonade. Sam’s expected revenue of $100 assumes he can sell 100 cups at $1 each, but a price rise to $1.20 might cut sales to 80 cups.
萨姆的柠檬水需求取决于几个因素。炎热的天气会增加对冷饮的渴望，使需求曲线向右移动。位于繁忙游泳池附近意味着许多潜在顾客会经过。然而，如果附近商店以更低价格出售瓶装果汁，一些顾客就会转而购买那种替代品，从而减少对柠檬水的需求。萨姆的预期收入 100 美元假设他能以每杯 1 美元售出 100 杯，但价格提高到 1.20 美元可能会使销量降至 80 杯。
Changes in tastes, weather, the number of buyers, and the price of substitutes all act as demand shifters in this simple business.
口味、天气、购买者数量以及替代品价格的变化，都在这个简单的生意中充当需求变动因素。
8. Supply and Costs Analysis | 供给与成本分析
On the supply side, Sam is willing to produce lemonade because the expected money profit is positive. The explicit costs – lemons, sugar, and cups – work out to $0.30 per cup. With a selling price of $1.00, his accounting profit per cup is $0.70. If he sells 100 cups, total revenue is $100 and total explicit cost is $30, giving an accounting profit of $70.
在供给方面，萨姆愿意生产柠檬水是因为预期的货币利润是正的。显性成本——柠檬、糖和杯子——每杯合计 0.30 美元。以每杯 1.00 美元的售价计算，每杯的会计利润为 0.70 美元。如果他售出 100 杯，总收入为 100 美元，总显性成本为 30 美元，会计利润为 70 美元。
However, from an economist’s perspective, the hidden cost of Sam’s time matters. His time could have been used for the coding camp worth $100. When the opportunity cost is included, the economic profit
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