Newbie: How do I calculate annualized performance of investments?

I think you are correct in assuming that's really an apples to oranges comparison. It generally doesn't make sense to compare two different investments over two different time periods. And generally it is not a good idea to try to annualize the returns of investments held less than a year.

It does, on the other hand, make sense to annualize the returns on investments held longer than a year for comparison purposes. They are most often compared against the annualized returns of a "benchmark" (for example, the S&P 500 index) for the same time period or another investment held in the same time period. If you encounter that situation, just post and I can suggest ways of calculating that in Numbers.

SG

By investments do you mean an investment portfolio or do you mean capital investments by, say, a company. Generally it's not meaningful (an in fact is frowned on in the investment profession) to annualize returns on investments held less than a year.

For investments held longer than a year there are various ways to calculate returns that generally do not involve the XIRR function. Do you have cash inflows and outfows (contributions and withdrawals)?

SG

It sounds to me like you are looking for the XIRR function. It exists in Excel, LibreOffice Calc, and Google Sheets, but not in Numbers for Mac.