How many people in the room is just enough?

Having more people does not make decisions more certain. It only slows everything down, blurs accountability, and creates what is known as false consensus (groupthink, where everyone nods along without truly analyzing). In any brand workshop, the right question is not "who should we invite to fill the room" but "who truly needs to be present for this meeting to reach a decision."

Two types of purposes, two ways of calculating people

Before counting heads, you need to determine what type of session this is.

• Decision-making session: requires someone with authority and someone who holds the data. The number of participants should be small enough for everyone to truly voice their opinions, not just to be present.
• Idea generation or broad feedback session: It can be larger, but small groups need to be formed for discussion before regrouping, rather than cramming everyone into one conversation.

Confusing these two types is the most common mistake. A decision-making meeting that is treated like a communication session often results in no conclusions being reached.

The number of communication lines increases exponentially

When adding one person to a room, the number of communication lines between members does not increase by one, but rather increases exponentially. Three people have three communication lines. Four people have six. Six people have fifteen. This means that each additional person complicates the meeting further in depth, not just adding another voice.

Thus, each person invited into the room must contribute their part: either they have data that others do not, or they have the authority to decide on part of the issue. If they are just sitting and listening, they should be moved to the group that receives results after the meeting, not the group sitting in the same room.

When to choose which direction

If it is a large organization and wants many voices involved, Sinh Vũ suggests a layered structure: a core round with fewer people to finalize direction, and additional rounds to gather feedback beforehand and communicate results afterward.

The core value of the small group principle is to keep the group small enough to avoid false consensus and maintain decision-making speed.

Practical interpretation from Amazon, J. Richard Hackman (Leading Teams, Harvard Business School Press)

Common errors when inviting people into the room

• Inviting enough voices: a room of twenty people where only five truly speak up. The remaining fifteen waste time and make the five more hesitant to express themselves.
• Confusing decision-making sessions with communication sessions: Turning a workshop (a structured working session to achieve results) into a one-way meeting where everyone attends but no one takes responsibility for decisions.
• Select an even number when a decisive outcome is needed: if there is a possibility of needing to vote or decide between two directions, an odd number of decision-makers helps avoid a tie.
• To let the big boss sit quietly and observe: when someone with high authority is in the room without clearly participating, the others often self-censor their opinions instead of speaking honestly.

The viewpoint of Sinh Vũ

Sinh Vũ does not conduct group workshops with more than twelve people because operational experience shows that beyond that threshold, the quality of discussion decreases significantly and it becomes difficult to keep everyone focused on facts rather than expressing opinions based on emotions or the most powerful person in the room. This is Sinh Vũ's operational limit based on real working experience, not a universal threshold applicable to all organizations.

What Sinh Vũ cares about is not specific numbers but principles: every seat in the room must have a reason. If you cannot answer "this person needs to sit here because they have what information or authority," then that person should be outside, not inside.