Question 151284
Out of 289 reviewed, you're % of error is,
{{{(12/289)100}}}=4.15%
Or,
{{{((289-12)/289)*100}}}=95.85% are right.
Of the remaining {{{925}}} you didn't review (1214-289) you assumed they're right.
The more glucose you review, the lesser your percentage of error if it remains at 12 errors. 
Thank you,
Jojo