I have a monthly report that lists transactional errors made by facilities all over the country. Each row is a single error and the columns represent descriptive information about each error (ID, geographic region (Group1), city (Group2), date transaction was created, etc). Generally, these reports have about 1500 - 2000 rows.
Here's a preview of what it looks like:
Obs_Num UniqueID Group1 Group2 CreationDate ReportDate DateDiff 1 654K34C 1 345 03/12/2018 04/01/2019 385 2 231U09R 1 654 06/17/2017 04/01/2019 653 3 144L77E 2 987 03/12/2018 04/01/2019 385 4 798Y65A 4 209 10/26/2018 04/01/2019 157 5 862H42J 5 654 02/27/2019 04/01/2019 33
We know a specific error has been corrected, when it does not appear on the next month's report. We send a summary of these reports out every month by totaling the number of errors by geographic region and then facility in a particular city. The hope is that with each report we send out the number of total errors decreases month by month. That's not always the case - sometimes the numbers go up, but most of the time they go down.
I want to do a survival analysis on these errors basically "surviving" until they are corrected. The event will be the correction and the "time to event" will be the time it takes until correction.
My plots all look reasonably correct and the results from doing a few Log-Rank tests made sense. However, my issue is with the time variable that I'm using. I have a designated point for when the time period for measuring whether or not an event occurs ends; the date the report was generated. But, most errors have wildly different creation dates. Some a few days before the report generation date, others a few years before the report generation date.
My question: In survival analysis, do I need to structure a dataset in which all errors (rows) have the same starting time periods? Or at least equal intervals? If that's the case, should I have ranges of 30 days in which an event can occur and then continue adding 30 day periods (or however many days in the particular month) as each monthly report is generated?