# Conditional probabilty help.

• Jul 16th 2011, 09:13 PM
university
Conditional probabilty help.
it has been observed that 45% of the email sent to your account is spam and as a result you have set up a spam filter.however the filter fails to quarantine 2% of spam emails and inadvertently quarantines 5% of genuine emails.
1)what is the probabilty that an email will be quarantined as spam?
2)if an email is quarantined as spam what is the probabilty that it is actually a spam email?

i tried this question and came up with 46.85% for part 1 and 94.13% for part 2 are these answers correct?
• Jul 17th 2011, 01:24 AM
mr fantastic
Re: Conditional probabilty help.
Quote:

Originally Posted by university
it has been observed that 45% of the email sent to your account is spam and as a result you have set up a spam filter.however the filter fails to quarantine 2% of spam emails and inadvertently quarantines 5% of genuine emails.
1)what is the probabilty that an email will be quarantined as spam?
2)if an email is quarantined as spam what is the probabilty that it is actually a spam email?

i tried this question and came up with 46.85% for part 1 and 94.13% for part 2 are these answers correct?

Please show your working - it makes it easier to check for obvious errors - should they be present - without having to spend time doing the calculation.
• Jul 17th 2011, 09:23 PM
CaptainBlack
Re: Conditional probabilty help.
Quote:

Originally Posted by university
it has been observed that 45% of the email sent to your account is spam and as a result you have set up a spam filter.however the filter fails to quarantine 2% of spam emails and inadvertently quarantines 5% of genuine emails.
1)what is the probabilty that an email will be quarantined as spam?
2)if an email is quarantined as spam what is the probabilty that it is actually a spam email?

i tried this question and came up with 46.85% for part 1 and 94.13% for part 2 are these answers correct?

You do realise that we could give a yes/no answer to this, and if it were no you would then have to ask a further question and if yes you could still get zero credit for this if the method you used was erroneous.

CB