There are only 7 inkjet brands:
Brother
Canon
Dell
Epson
HP
Kodak
Lexmark
Of the above, ALL Epson, ALL Kodak and ALL Brother have printheads in the printer. So that covers almost 50%.
The other 50% depends on what the cartridge looks like. If its a "tank style" cartridge, which looks like this:
This means printheads are in the printer.
If the cartridge looks like this:
the printheads are on the cartridge.
WHAT IS THE SIGNIFICANCE?
If there is a quality issue with your printing, you should print a nozzle test. This will diagnose if there is a clog in the printheads.
If the nozzle test shows a clog, and the printheads are in the printer, you can attempt to UNCLOG the print heads by running a "cleaning cycle" on the printer. Some printers have varying levels of cleaning cycles, such as "cleaning" and then "deep cleaning" and then "deeper cleaning". You should run 2-3 cleaning cycles, and deep cleaning if its an option.
If the nozzle test shows a clog, and the printheads are on the cartridge, your only option is to try unclog the cartridge by wicking the printheads on a wet/damp paper towel (wet with alcohol is best, or use Uni-Kit printhead cleaning solution). If that does not resolve the clog, then the cartridge should be replaced.