We also know there are known unknowns; that is to say we know there are some things we do not know.

我们也知道还有一些已知的未知，也就是说我们知道自己还有一些不知道的事情。

youdao

Today we have new uncertainties. I made a quick list of current known unknowns in my own mind.

如今我们有了新的不确定性，关于当下的已知未知数在我的脑海里列了一张快速名单。

youdao

There are known unknowns. That is to say there are things that we now know we don't know.

世界上有已知的未知，也就是说我们知道我们还不知道的那些事情。

youdao

Just what proportion of trials are kept under wraps is unclear - one of Donald Rumsfeld's known unknowns - but a 2010 study from the National Institute of Health Research suggests that half are never published, and those with positive results twice as likely to get into print.

BBC: Trust of medical volunteers 'betrayed'