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The original link: mp.weixin.qq.com/s/b8BfWCdb9… Author: Gong Jin

The principle of MECE

The MECE principle (Mad Exclusive, Collectively) is by no means Exhaustive. In short, this rule is consistent with no overlap, exclusion, and completeness.

Just like cutting a pizza, a large pizza, cut into 8 pieces with 4 knives, each piece does not overlap with each other (exclusive), together can restore the large pizza.

MECE principle is a structured way of thinking proposed by McKinsey. It is a good way of thinking for report writing, proposal presentation and business analysis.

Let’s look at an example.

The price of park tickets. Admission to the park is 20 yuan, and the concession includes both senior and children’s tickets. The price system is:

  • Children under 10 are free;
  • Half price for minors over 10 years of age;
  • Free for seniors aged 60 and above;
  • No discount for other adults.

If we look at the pricing system here with MECE principle, we will find that the system has “omissions” and “incompleteness”. For example, is 10-year-old Xiao Lin included in the free range for those under 10 years old, or in the half-price range for those over 10 years old?

In programming language, the code corresponding to the above prices is:

Org_price = 20 age = 10 if age < 10: discount = 0.0 if age > 10 and age < 18: discount = 0.5 if age > 60: Discount = 10 if age >= 10 and age < 60: discount = 10Copy the code

Obviously, when age is 10, the program doesn’t follow any of the policy branches, so the code gets an error.

When solving similar logic problems, it is important to note all the possibilities of boundary values. In principle, each feasible value (especially the boundary value) can and can only fall in one policy branch.

A common analysis method is the line drawing method, as shown in the figure below. Draw a number line representing all possible values, and then use the if statement to break down the problem, with hollow points representing the open interval and solid points representing the closed interval.

Logical calculation: “and”, “or”, “not”, “xOR”

A proposition is a statement that describes an objective thing and contains the possibility of being right or wrong.

  • If the statement is correct, we usually usetrue 或 1To represent;
  • If the proposition is wrong, we usually usefalse 或 0To represent.

With propositions, we can make logical calculations about propositions and propositions. Just like when you have numbers, you have addition and subtraction.

Logical operations usually have “and”, “or”, “not”, and “xor” superimposed on top of this.

The most basic “and”, “or”, “not”.

  • Logical and

A and B, A and B are true only if both A and B are true, otherwise both are false;

  • Logical “or”

A or B, if either statement A or statement B is true, A or B is true, otherwise false;

  • Logical “not”

Not A, not A is true when statement A is false, false otherwise.

“Xor” from Venn diagram

“Xor” is also called A^B in Python. If statements A and B are not true or false, then A^B is true, otherwise false.

Venn diagram is used to demonstrate the operation process of “and” “or” “not”.

  • “And”A and B

According to the definition of the logical operation, as shown below, the region where A and B are true is the intersection of ellipses A and B (the blue region).

  • “Or”A or B

As shown in the figure below, the region where A or B is true is the union of ellipses A and B (the blue region).

  • “Not”not A

As shown below, the region where not A is true is the part outside of ellipse A (the blue region) :

  • “Exclusive or”A^B

A^B is the blue area of the following Venn diagram.

And you can see that the blue region of A to the B is the region of A or B up here minus the region of A and B, so A to the B is equal to A or B minus A and B.

From logistic regression to communication

We use related words in everyday communication, such as “and” “or” “but” “if… So…” “Because… So…” What do they have to do with and or not? We combine logical operations with Venn diagrams.

1. And/or

“And”, as the name suggests, is A and B. For example, xiaolin is beautiful (A) and Xiaolin is smart (B). After A logical operation, xiaolin is beautiful and smart (A and B).

Or, as the name suggests, A or B. For example, this summer, Xiaolin plans to go to Hainan, otherwise Xiaolin plans to go to Liaoning, after the logical operation, xiaolin plans to go to Hainan or Liaoning (A or B).

When you use “and” and “or” to communicate, you should note that propositions A and B are independent of each other, that is, A and B should conform to the “non-repetition” principle of MECE mentioned above.

Here are three counterexamples:

Example 1, Xiaolin is smart and beautiful (A), and Xiaolin is smart (B).

While semantically correct and understandable to the reader, from a communication point of view, this sentence is very inappropriate.

Example 2, in order to ensure A stable transition of the system (A), and (i.e., “and”) to ensure that the requirements of the various users are normally iterated during the transition period (B).

In this case, proposition A obviously includes proposition B.

Example 3, Xiaolin is from the northeast (A), or Xiaolin is from the north (B).

The word “north” contains the word “northeast”, repeating each other, taking a big detour in the expression, only expressing that Xiaolin is from the north.

Through these three counter examples, we can see that, although the lack of logical correlation words does not affect the correctness of semantic expression, they will make communication jumble and not straightforward enough, thus reducing the efficiency of communication.

Therefore, communication and expression are directly related to logical thinking.

2. Because… So…

The associated phrase is A logical inference that follows from A to B.

After using “because… So…” When communicating, we must pay attention to whether there is sufficient causal relationship between propositions, otherwise, there will be logic errors that make people disgusted.

Here’s a good example:

Because Xiaolin is smart and beautiful (proposition A), xiaolin is beautiful (proposition B).

It can be seen that both propositions A and B have sufficient causal relationship of inclusion and inclusion.

Here’s another counterexample:

In order to ensure the stable transition of the system, and ensure that in the transition period, the needs of each user normal iteration, so the system is divided into three phases: transition period, experimental period, switching period.

That is, to ensure a stable transition, so split into three phases.

So to ensure a stable transition, must it be split into three phases? Obviously not, split into four phases, five phases, all depending on the developer’s own design scheme, is ok, obviously there is no strong causal relationship between the two. You’re not going to be convincing when you present your proposal.

3. Although… But…

It represents a transitional relationship.

For example, people who work hard (B) may not do well in school (not A), which forms A turning point. Therefore, xiaolin does not get good grades (not A), but she works hard (B).

As is shown in the picture below, you will find that “although (not A)… But (B)…” This correlation is related to “because (A)… So (B)…” Just the opposite. “B because of A” can also describe “not A, but B”.

So we can test “although…” by turning it into a causal relationship. But…” Whether or not this correlation is properly used.

For example, although Xiaolin is not single (not A), she is A native of northeast (B).

Because Xiao Lin is single (A), she comes from northeast (B). Obviously, there is no causal relationship, so the original sentence is problematic.

Although Xiao Lin did not get A good grade (not A), she did not give up on herself (B).

Because xiaolin got good grades (A), she didn’t give up on herself (B). Obviously, there is a strong causal link here, and it can be argued that the “but” in the original sentence is quite appropriate.

Although Xiaolin is not single (not A), she still gets good grades (B).

Because Xiao Lin is single (A), she gets good grades (B). Here causality is weak, so the use of “but” is not entirely appropriate.

In fact, in our daily life, there are many times when the “but” is misused. Although there is no need to pay too much attention to these flaws in daily communication, such expressions are not appropriate in the context of written language.

conclusion

How to speak logically?

When you master a good way of logical thinking, you will be more convincing in communicating with others, and your communication efficiency will be greatly improved. When analyzing things and problems, they will be more thorough and perfect and get to the point.

If you look at the examples above from a logical point of view, especially if you have used Venn’s diagram, you can clearly see where the logical relationship between these sentences falls apart.

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