Settings > General > About > Diagnostics & Usage > Diagnostic & Usage Data
I've elected not to send this data to Apple, so is there a way to clear or delete it?
They are usually deleted when you do a sync.
In iPhone 5s iOS 9.2 go to Settings->Privacy and go the last part of the menu ->Diagnostic & Usage. Then select which one you want.
Make sure your iPhones is backed up ! Then then General , master reset that clears everything and reset your iPhone back to its original setting, then start your iPhone just like it was a new one ! Once it's has the wifi set up all your information goes back on your iPhone but not the diagnosis & usage ! I have to do this about once every few months to keep my iPhone 6plus s running fast , this works the fastest for me and all you need to have is a Wifi connection ! Time it takes me is 6 to 15 minutes max , your reset may take less or more time depending on the information that you have stored on iCloud !
Open iFile. Go to var/mobile/Library/Logs/CrashReporter and delete all files leaving the 3 folders undeleted. Done.