CASE: There is a Starbucks in the building you work. You stepped out for lunch one day and noticed that there was an extra long line of customers outside this Starbucks. The question is what do you think he reasons are.

这个case的答案可以有很多种，我想讲的不是具体答案的内容，而是找到答案的approach。

这道题有三个品阶的答案，一为下乘，是laundry list；二为中乘，以visualization或者其它某种逻辑进行组织的list；三为上乘，不但把绝大多数factor都通过visualization或者其它某种逻辑identify出来，还会在present的时候赋予priority。

第一种答案looks like this：The line is long maybe because there is a sale going on in the store. It can also be because the cappuccino machine is broken. Maybe, it’s just a random moment when there happens to be a lot of customers.

第二种答案的looks like this：I think there can be many causes. Let me walk you through the causes by visualizing the scenario. When I look at the line outside Starbucks, I notice the weather, it could be a hot summer day or an extremely cold winter day, and the weather drove people to get in line for a cool or hot beverage; when I look closer at the line, I notice there are a lot of people wearing similar name tags from a conference, so the line is long maybe because there is a special conference taking place nearby; I jumped into the line and stepped in the café and noticed that there is a special promotion going on at the merchandize section; as I move closer to the menu board, I notice that new items are added to the menu, for example, hot sandwiches, which takes a lot longer to make; as I approach the cashier, I notice a new technology is adopted and the cashier seems to be having trouble using it; I also peek into the kitchen, and notice that the barista keeps running back and forth from the new fridge and the cappuccino machine for fresh milk; lastly, after I get my drink, I notice that a lot new tables and chairs are added to the café so the indoor space for lines are squeezed.

第三种答案looks like this:

I think there can be many causes, but some are more important than others. I’d like to categorize them into internal and external causes. Let me walk you through my internal causes first because they may have more implications for Starbucks, and then I will walk you through the external causes.

For internal causes, I have two main categories: products and operation. For products, I have offerings and pricing. What I mean by offering is, for example, Starbucks may have added some food to their menu that takes a lot longer to make, like hot sandwiches, or they may have special drinks offered in a limited time; for pricing, there may be a promotion   going on food, drinks or merchandizes. Under operation, I have store, cashier and kitchen. What I mean by store is operation hours, for example, if Starbucks reduced the hours they are open, they may have accumulated a lot of customers by the time they open their store; by cashier, it is a key point where people make orders and pay for their orders, if the technology for ordering and payment is problematic or the cashiers are not well trained, it can delay the process; by kitchen, what I have in mind is how fast products can be made, which involves the layout of the kitchen and the skillfulness as well as staffing in the kitchen. 

The above are the internal causes. On the external side, I have general environment and customer. General environment includes weather and outside competition. Customer include regular and irregular customers. Weather can be extra hot or cold and increase the demand for cold and hot beverages. Nearby café may have closed which pushed customers to this Starbucks. Regular customers may just happen to show up on the same time, or we may have irregular customers like tourists in town or business men in town for a conference.

Different factors have different implications for Starbucks, and I can go deeper into each if you want.

三类答案的对比其实已经非常明显。这个case的teaching point有三：1. Visualization是确定key factor的很有用的工具；2. Structure, structure, structure；3. You need to have a priority when structuring your response.

有过一些casing经验的同学，一般都知道要structure，但是其实只structure是不够的，你的structure要有重点。很显然，突然一天的conference in town对Starbucks的经营是没有太大的意义的，而因为改变菜单而增长了队伍，肯定是对net profit有关键性影响的。所以如果你只依靠visualization，那么你就会把conference in town这种没有太大战略意义的答案放在前面，如果你structure，你就会把它放到后面一笔带过。Laundry list我就不做太多评论了，它是一个巨大的坑。每当你发现你在给你的interviewer列laundry list的时候，你就该马上打住, nothing kills a case interview more than a laundry list does.

做case的opening的基本原则是MECE structure，这个我以后会花很多时间来和大家讨论，目前阶段我觉得要把一些重要的intuition建立起来，欢迎大家问问题，当然也欢迎大家post自己的答案。

给出第三个答案的基础是你可以迅速的利用visualization在脑海里把key factor找到，然后再迅速的recategorize，赋予其priority。这个skill是贯穿整个case interview的。让你给出第三类答案的时间其实就只有两分钟