But that still does not make sense, lets say you fail a day at 20% error rate. this means you are still up 80% of that day which means that the total that should listed as failed for the week would be 5%. under your way of calculating you are stating that it is 20% of a week. Why are you being so hard on yourself? =) also if the SLA is termed monthly that 20% down you had on monday if the only downtime would not be consider a failure of the SLA at all whereas calculating your way could make it a failure for the full term of the month depending on your SLA levels. Also very poor response times for 1 or 2 hours in the morning could scale your whole day as a fail even though the actual "outage" would only be < 10% of the day. seems like you are trying to prove your SLA's are failing to be met to me. =)

-Waswas