Mariano Sigman and Dan Ariely : How can groups make good decisions?

I'm sorry that I misunderstand the article. I fixed all. 13/3/2018
Mariano Sigman and Dan Ariely
How can groups make good decisions?
Summary
Although the speaker is speaking to us gently, this problem is difficult.
It's because the decisions we make in groups goes very wrong sometimes.

We, as societies, have to make good decisions collectively, but the wisdom of the crowds is destroyed by peer pressure, publicity, social media, or even simple conversations that influence how people think. If one person has a very confident decision or a higher position, people will follow him/her. When people debate in small groups, it seems to go better judgment, but our social and political issues have a lot of diverse opinions. When there is a moral question, people are more diverse. Thus polarized decisions won't help us.

However, it turned out that in the broad diversity groups, groups’ decisions reached a consensus even when they were composed of people with completely opposite views. It's because there are the middle people who are very confident, they understand that both arguments have merit, and they are much more likely to reach consensus.
Although the situation needs to be researched more,  what intuitive ideas are, who has confidence and who is believed seems to relate. 
It leads to robust average individually and spontaneously without any hint.

The speaker summarizes that good collective decisions require deliberation and diversity of opinion.
It will be effective in balancing between forming small groups that converge to a single decision and maintaining diverse opinions because there are many independent groups. 



Mariano Sigman and Dan Ariely at TED Studio  22/12/2017
How can groups make good decisions?
Summary
How can groups make good decisions? (transcript)
The answer that the speaker tells us is that it requires deliberation and diversity of opinion.
It'll be effective when there is balancing between forming small groups that converge to a single decision and maintaining diverse opinions.
It's because there are many independent groups and it's found that groups’ decisions reached a consensus when there are middle people in the group even with completely opposite views.
If small groups make good decisions, but it won't help us because our social and political issues have a lot of diverse opinions.
Those situations need to be researched more, because our intuition, who has confidence and who is believed are thought to influence to make good decisions.
Our decisions are always destroyed by peer pressure, publicity, social media or even simple conversations that influence how people think.
We have to use science more to make good decisions and we have to think what groups we are.

Words in this story
deliberation /noun/ long and careful consideration or discussion.
consensus /noun/  agreement, harmony, concurrence, accord, unity