Answer
When several materials can be substituted, the usage variance splits into a mix variance—the effect of using a different proportion (mix) of materials than standard—and a yield variance—the effect of getting more or less total output from the total input than standard. They analyze efficiency where inputs are interchangeable (e.g., food, chemicals).
Mix: (actual mix - standard mix) at std prices.
Yield: (actual yield - standard yield) x std cost.Real-world example A cheaper mix of ingredients gives a favorable mix variance but may worsen the yield.