## Sample Guesstimate Questions

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The guesstimate question (market sizing or other) is one of the types of question you are likely to encounter in consulting interviews.

Below we list twenty three (23) sample guesstimate questions broken down by question type.

## Population Questions

1. How many births are there in America each day?
2. How many petrol stations are there in Sydney?
3. How many bottles of wine are consumed in France each month?
4. How many cups of tea are drunk in England each day?
5. How many pounds are spent on haircuts in the UK each year?
6. How many weddings are performed in China each year?
7. How many men’s suits were sold in the United States last year?
8. Surfboards Inc. imports surfboards into America. Demand depends on the weather and the company needs to order stock six months in advance. How many surfboards should they order?
9. Estimate the total revenues obtained from the Harry Potter movies.
10. What is the size of the market for mobile phones in America?
11. How many cars are sold in in Australia each year?
12. How many people are buried each year in England?
13. How many taxis are there in New York?

## Household Questions

1. What is the annual market for apples in America?
2. What is the annual size of the market for golf clubs in Japan?
3. What is the annual revenue of Harrods in London?
4. What is the market for bicycles in America?

## Preposterous Questions

1. How far does the average Premiership footballer run in a game?
2. How much does Mount Kilimanjaro weigh?
3. How many ping-pong balls will fit inside a 747?
4. How much does a 747 weigh?
5. How many slices of pizza does it take to reach the moon?
6. How many tennis balls fit in a swimming pool?

## Approaching the Guesstimate Question

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A guesstimate question can be approached by breaking a question down into smaller pieces by asking the interviewer questions and making a series of narrowing assumptions.

You can break a question down either by starting big (e.g. making an assumption about the total population) or starting small (e.g. making assumptions about the average household or some other piece of the whole and then extrapolating).

After coming up with an estimate, it is a good idea to sanity check whether the estimate is in the right ball park by establishing reasonable upper and lower bounds within which the answer should fall.

There are three types of guesstimate questions that you might come across: population questions, household questions, and preposterous questions.

For population questions, the standard formula for calculating the market size is the following:

In finding the market size, segmenting the population using simple demographics will normally be the way to go. You might decide to segment the population by age group, gender, geography, income, or marital status.

## Guesstimate Questions

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The guesstimate question frequently comes up in consulting interviews.

It will often be a market sizing question, which may be a standalone question or part of a larger case question.

## What will you be asked to do?

The typical guesstimate question will require you to estimate a number by doing a rough “back of the envelope” calculation. You are supposed to reach a final answer by using a series of narrowing assumptions.

Your assumptions should have a sound basis and you should explain the logic behind your assumptions, however it is not important that your assumptions be 100% accurate.

## What is being assessed?

The guesstimate question is quite different from the kind of interview questions that you are probably used to.

For the guesstimate question, it is better to arrive at the wrong answer with good assumptions and clear logic than to know the right answer because you read it in a text book.

## 12 Tips for Nailing the Guesstimate Question

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Below we outline twelve (12) tips for nailing the guesstimate question:

## 1. Practice

Practice doing some guesstimate questions before the interview so that you are prepared. It is a good idea to bring a pen and graph paper to the interview so that you can keep track of your calculations.

## 2. Know some basic facts

Below are some facts that you should know. In addition, you should also know the key demographics for the country where you are interviewing.

## 3. Use round numbers

You are responsible for doing the calculations so pick numbers that are easy to work with. For example, estimate the population of America as 300 million not 316.1 million.

## 4. Clarify units of measurement

You should clarify the units of measurement that the interviewer wants from you. For example, market size can be measured by revenue or sales volume.

## 5. Take a moment

It is important to maintain your composure so before starting to answer the guesstimate question take a moment to write down the key details of the question, and consider your approach.

## 6. Have a clear approach

It is important to have a clear approach to help you answer the question. More on this in a later post.

## 7. Ask questions

Your interviewer may be able to provide you with direction. If the question is “How many ping-pong balls will fit inside a 747?” the first question you might ask is “What is the volume of a ping-pong ball?”

## 8. State your assumptions

The interviewer may not know the answer or may not want to give you direction so you’ll have to make assumptions.

It is a good idea to clearly state your assumptions. For example, “let’s assume that the diameter of a ping-pong ball is 4cm. The formula for the volume of a sphere is 4/3.pi-r^3. So the volume of a ping-pong ball would be about 11-pi centimetres cubed”.

## 9. Think out loud

The interviewer is trying to assess your thought process in getting to the answer, not the answer itself. If you don’t think out loud, you make it difficult for the interviewer to give you points.

## 10. Explain your logic

As you make your way through the problem it is helpful to explain the logic behind each of your assumptions.

Instead of saying “a 747 is about 100 metres long” you could say “I know that an average car is about 5 metres long and based on my experience I would say that 20 cars lined up end to end would be about the same length as a 747. So I will assume that a 747 is 100 metres long”.

## 11. Answer the question

After doing all of the calculations remember to answer the question that has been asked.

## 12. Be prepared for follow-up questions

After you answer the guesstimate question, the interviewer might ask “If you had to find the real answer to the question, how would you do it?” This is a test of your creativity and resourcefulness.