Hello MathHelp World,

I have a survival function that estimates the amount of time that a message remains unopened once dispatched. (See attachment) The data is shown on the left, for instance, after one day, 87% of messages remain unopened, and after 3 days 83% remain unopened.

After 30 days the messages expire and they are pulled. At that point in time about 47% of the messages were not opened.

I fit a polynomial function to the curve and figured a definite integral over the 30 day time frame. The result was about 19.

My question:

What are the units and how can I use this information? This is 19 'Days'? 19 'Message Days' Can I say that the messages are in the system for an average of 19 days? If I have a system capacity of say 100 messages, and I dispatch 50 messages that I expect will remain in the system for an average of 19 days, can I say that it is using an estimated (19/365) * (50/100) = 2.6% of the annual message capacity?

Any help appreciated,

Will