McKinsey PST 10: Necessary and Sufficient Conditions - Fless
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# McKinsey PST 10: Necessary and Sufficient Conditions

What does ‘a critical factor’ mean? If having a Harvard MBA were a critical factor for getting into McKinsey, would that mean Harvard alums would 100% get in?

00:20 Example 01

02:09 Necessary Conditions
03:15 Sufficient Conditions

04:25 Example 02

04:53 Summary

[TRANSCRIPT]
Necessary and sufficient conditions is the topic of the 10th theory session of the problem-solving test course.
We will learn what the critical factor is, discuss the concept and learn how to identify it in test questions.
Here’s an interesting example from an official PST
You might want to pause the video now and try to solve the question on your own. Which of the following statements is accurate?
regarding the gallery’s bid for additional funding? Option A. If the gallery has provided economic benefit to Riverside, it will receive additional funding from the Arts Council. Economic benefit results in funding. Option B. If the gallery has not provided social benefit to Riverside, it will not receive additional funding from the Arts Council. Option C. If the gallery has not provided economic benefits to Riverside, it will not receive additional funding from the Arts Council. If the gallery has provided social benefits to Riverside, it will not receive additional funding from the Arts Council.
We’ll look at the text and learn what is important for getting that funding. From the text we learned, that the gallery’s management in order to get funding will need to prove to the Arts Council that the gallery is benefiting the local area of Riverside and it needs to benefit in two ways: economic and social.
We also learn that economic benefit to Riverside is the critical factor that will determine whether or not they will receive additional funding.
Critical factor is the necessary condition. And necessary condition means, that lack of necessary condition brings lack of result. In other words, no economic benefit means no funding and this is exactly what is said in the option C. Option C is right.
Let us have a look at necessary and sufficient conditions in more detail.
Necessary conditions. Condition A is necessary for condition B, means that absence of A results in absence of B. Equivalently, it means that presence of B is possible only if A’s present, it does not mean that presence of B results in presence of A, because some other conditions might be necessary.
Words such as critical, vital, essential, imperative, obligatory and so on are indicators of necessary conditions.
Let’s consider these hypothetic statements which is of course not 100 percent true in reality.
Having an MBA is a necessary condition for an associate position at McKinsey.
Based on this statement we can conclude that if you do not have an MBA you will not become an associated McKinsey. If you have an MBA you might still not become an associate, probably because there are other factors at play. But if you got an associate position you must have had an MBA.
This is how necessary conditions work. Now sufficient conditions. Condition a is sufficient for condition B means that presence of A will guarantee presence of B. Equivalently, it means that absence of B is possible only if A is absent.
It does not mean that absence of A results in absence of B.
Maybe some other condition is enough not just condition A. The indicators of sufficient conditions are words like: enough, to assure, to ensure, to guarantee, to lead to. Continuing our hypothetic McKinsey story.
Let us have a look at the following example. An MBA with distinction from Harvard guaranties an associate position at McKinsey.
Based on the statements we can conclude that if you have an MBA with distinction from Harvard you will get an associate position McKinsey.
If you don’t you still might get it but most probably other conditions will apply.
And if you did not get an associate position with McKinsey you had not received an MBA with distinction from Harvard either.
So much for sufficient conditions. Take a moment to think which option an accurate statement is now. This time we notice that proven economic benefit to Riverside is a sufficient not necessary condition for funding.
That means that presence of economic benefits will lead to additional funding.
And this is exactly what option A is saying now. And this time, option A is accurate.
Let us synthesize what we have today. A necessary condition is a must have for achieving a certain result.
However, it might not be enough. A sufficient condition on the contrary is enough for achieving a certain result.
However, it might not be a must have. Once again have a look at the indicators words and make sure to notice them in the actual PST. That’s all for today.