10% of all email you receive is spam. Your spam lter is 90% reliable: that is, 90%
of the mails it marks as spam are indeed spam and 90% of spam mails are correctly
labelled as spam. If you see a mail marked spam by your lter, what is the probability
that it really is spam?
(a) 10% (b) 50% (c) 70% (d) 90%
10% of all email you receive is spam. Your spam lter is 90% reliable: that is, 90%
of the mails it marks as spam are indeed spam and 90% of spam mails are correctly labelled as spam. If you see a mail marked spam by your lter, what is the probability
that it really is spam?
(a) 10% (b) 50% (c) 70% (d) 90%
0 Replies
engineer
1
Reply
Tue 8 Apr, 2014 06:12 am
@keydee,
Let's say you get 1000 emails.
100 are spam, 900 are not.
Of the 100 that are spam, 90 are marked. (90% accurate)
Of the 900 that are not, 90 are marked. (10% error)
So 180 are marked of which 90 are truly spam -> 50%
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