When numbers play a significant role in the process of decision making, it is natural for the human mind to employ the technique of estimation- a method that will yield a value that is correct enough but not actually correct. Over the course of scientific development and progress, the need for unique and simple procedures to determine the approximate figures arose, and with the utilization of insightful and intuitive approaches by experts over time, a few methods have risen to the surface and remain essential in practical use. A chief example for this, is the process of Guesstimation.

A portmanteau of ‘guess’ and ‘estimate’, the implied meaning of ‘guesstimation’ is rather evident- an estimate made without using the complete information, involving some kind of guesswork, usually an informed or educated guess. The concept, coined by American statisticians in the mid-1930s holds a lot of value in the industry today, when it is often imperative to arrive at the tentative completion date for a project or the rough budget for an event.

Guesstimation is closely associated with some other forms of approximation and solution-finding methods such as heuristics, trial and error, Back-Of-The-Envelope (BOTE) calculations and Scientific Wild-Ass Guessing(SWAG). These approaches on the whole aim to find a solution (based on expertise in the field, past experience and intuition) that will be valid enough for the desired result but can be optimized further.

‘*Guesstimation: Solving the World’s Problems on the Back of a Cocktail Napkin*’ , a book by Lawrence Weinstein and John A. Adam of Old Dominion University gives many examples of guesstimation problems and shows the reader how seemingly interesting inferences can be drawn from simple observations.

**Why is guesstimation an essential skill?**

Guesstimation involves a lot of logical thinking and mind-mapping, and requires one to analyze and think about the different ways of approaching a single problem. Observing how a candidate comes to a certain conclusion based on various logical deductions can expose to the potential employer, how well the candidate will be able to perform in the future. The specialty about this skill is that, it is independent of industry- it is merely a benchmark to decide if the candidate is capable of coming up with a solution to every problem. The interviewer will gain a great insight about the thinking capability of the candidate.

This skill is crucial for successful market fixing, wherein a quantitative variable namely the size of a particular market is determined based on known facts and their rough approximation, often employing scale (or order-of-magnitude) analysis. It is also used for scientific calculations and approximations. Guesstimating enables one to understand and analyze the magnitude of a particular entity without facing hassles in the form of tedious calculations that yield the precise answer.

The knack of guesstimating can prove to be extremely useful for project managers who might have to analyze the different parameters associated with the completion of a project to arrive at its tentative submission date. It is often more imperative for scientists and researchers to be able to guesstimate, for this will help them determine if a certain result obtained lies is in the correct range.

Testing the guesstimation skills of a candidate not only adds depth to the recruitment process, but also acts as a guiding light to choose the best candidates. It makes sure that the testing process truly serves its purpose and brings to the forefront the full potential of the prospective employee. Hence, guesstimation should certainly be included as a parameter to test the skill of any technician.

Guesstimation in a nutshell

**How should one attempt to solve a guesstimation problem?**

Though it might seem quite intimidating to try to deduce for instance, the number of dogs in the country or the number of people wearing black on a typical Wednesday, there is a fairly simplistic and methodical way of approaching these problems. The key is to look for the possible parameters that may affect the desired output and estimate the necessary values.

- First, the given facts should be clarified and all the available resources that are relevant to the problem should be gathered.
- Then, the concept of modularity should be employed to simplify one big problem into a bunch of smaller problems.
- Now, each of these should be solved using relevant assumptions and numerical approximations.
- Lastly, the final result should be consolidated.

Consider the following problem statement:

*Find the number of people wearing a blue band.*

**Solution:**

**Step 1: ***The facts need to be clarified.*

*Total number of people in the world or in this country?**What is the age group of the people under consideration?**What does band mean-hair band, elastic band, wrist band?**What does blue mean-does it include all shades of blue or just a particular shade?*

*Now let us assume the facts have been clarified to be the following*

*The problem is concerned about people of this country.**The age group is 5-50.**Band refers to a wrist band.**Blue can include all shades of blue.*

**Step 2: ***The problem should be broken down.*

*Find the number of Indians (assuming the country to be India) in the age group 5-50.**Find the chance that someone would adorn a wrist band.**Find the chance that a given wrist band is blue.*

**Step 3:***These problems should be solved using relevant assumptions and approximations.*

*The population of India is roughly 1 billion.**Around**65% of the population is under 35 years of age. So, the percentage of people in the age group 5-50% can be assumed to be about 70%.**There are more chances of people in fashion and sportsmen sporting a wrist band. Since sports is not a very popular career choice it could account for 10%, and since fashion and entertainment is slightly**more popular, it could account for 15%, summing up to 25% of the total population.**Since blue is one of the primary colours, the chance of the wrist band being blue in colour is 30%.*

**Step 4: ***Now the final result should be arrived at.*

*The total number of Indians of the age group 5-50 wearing a blue coloured wrist band*

* = 1 billion x 70% x 25% x 30%*

* = 52.5 million *

Note that it is not essential for the answer to be correct or even remotely accurate. The method of solving the problem has more importance than the solution itself.

Some pointers to grasp the knack of guesstimating:

-> Use scale analysis and appropriate numerical approximations.

-> Use trial and error.

-> Arrive at a Ballpark figure!

The aim of this article was to drive home the point that guesstimation is immensely essential in the present day scenario and that it is imperative to test this skill to determine who the better candidates are, in any testing process. So go ahead and master the art of guesstimation, for it will help you in one way or another!