When a product is in the first stage of development, there is often no actual product idea to evaluate. Through exchanges of ideas and group techniques, one can arrive at realistic alternatives which can be evaluated with the help of other methods. Subjective methods can also be used to evaluate the usability of prototypes or software products. Users can be asked about how they experience the actual or proposed product. There are also methods to rate or scale experienced satisfaction on one or several products.
Some methods give qualitative information on how the user experiences a specific product.
Subjective tests are used as a rule, to compare several products, but they can also be used to identify problems in the dialogue between man and machine.