The phrase "diversified mix" means having a variety of different things or elements. It is a combination that includes different types, so it is not limited to just one kind. Full definition
Investing strategies should start with a broadly diversified mix of stocks, bonds, and cash, based on your goals, feelings about risk, financial situation, and investment timeline. (fidelity.com)
The book urges investment in 12 index funds, which gives a very diversified mix. (alephblog.com)
A target date fund provides a professionally diversified mix of investments all within one fund. (blackrockblog.com)