Generally speaking, financial instruments which are characterized by high risk are usually associated with high returns. Similarly, those characterized by low risk are usually associated with low returns and so on. Therefore, based on the behaviour of the markets or underlying instruments of the various types of investments, the risk/ reward profile can be ascertained.
For example, stocks (traded in a highly volatile market) are considered high risk and is associated with very high returns over the long term. Meanwhile, other types of investments whose markets tend to be less volatile are associated with relatively lower returns.
Stock: High potential returns
Bonds: Moderate potential returns (depending on bond type)
Mutual funds: Moderate to high potential returns (varying by type of Fund)
Unit trusts: Moderate potential returns
Investment-linked insurance: Low to high potential returns (depending on type of investment)