Is there a perceptible sensory difference between products?
In what way do 2 lasagnes differ?
Is there a perceptible difference between water from a glass bottle and water from a plastic bottle?
Is margarine A a good match for margarine B?
Can I replace a raw material without the end consumer noticing?
Does a new machine affect the end product?

Tools: scoring test - triangle test - ranking test - multiple comparison test - paired comparison test - difference from reference test