[thedevopsguy]

My brain is shutting down and I can't parse this phrase.

[1] "If you lack an antigen that 99 per cent of people in the world are positive for, then your blood is considered rare."

[2] "If you lack one that 99.99 per cent of people are positive for, then you have very rare blood."

Surely the author is saying the same thing here?

[DaFranker]

They're two different official categorizations.

"Rare" = 99 in 100 people have this antigen, while you do not.

"Very Rare" = 9999 in 10000 people have this antigen, while you do not.

That's all it says.

If you lack an antigen, but at least 1 in 100 other people also lack this antigen, then your blood is only of the "Rare" category. If you lack an antigen and you'd have to go through 10 000 other people to find someone else lacking this antigen, your blood qualifies for the illustrious title of "Very Rare".

[gatehouse]

They are just quantifying the terms rare and very rare.

Rare is 1 in 100, very rare is 1 in 10000.

[dragonwriter]

Defining different degrees:

[1] 1 in 100 --> rare

[2] 1 in 10,000 --> very rare

[ManFromUranus]

number 2 has an extra .99 percent, so I guess in point 2, only 0.01 percent of people will have it (whatever IT is), vs 1 percent of people having the thing in point 1.

[thedevopsguy]

Missed the extra 9. Read and re-read. sincerely thought he called two identical categories rare and very rare.

Long day

thanks.