Scenario 2 – Sweetness of Sugary Drinks

You work for a major drinks manufacturer, but the government has introduced legislation that states your products must have sugar levels at a much more reduced level. You have been tasked with establishing a sugar content level that does not perceptually differ from the current sugar levels. So you design an experiment that utilises the Method of Limits to determine how sensitive individuals are to changes in your drink. You use the current drink as a standard stimulus, and you have a number of comparison drinks with more or less sugar in them. Participants have to decide if the comparison stimulus has a higher sugar content (H), the same sugar content (S), or is lower in sugar content (L) compared to the standard. Here is a typical set of results from one of the tasters:

Sugar content (grams per litre)	A	D	A	D	A	D	A	D	A	D
56.0						H
54.0		H				H		H
52.0		H				H		H		H
50.0		H		H	H	H		H		H
48.0		H	H	H	S	H	H	H		H
46.0	H	S	S	H	S	H	S	H	H	S
44.0	S	S	S	S	S	H	S	S	S	S
42.0	S	S	S	S	S	S	S	S	S	S
40.0	S	S	S	S	S	S	S	S	S	S
38.0	S	L	S	S	S	S	S	S	S	S
36.0	S		S	L	S	L	S	L	S	S
34.0	L		L		S		L		L	L
32.0	L		L		L		L		L
30.0	L		L		L		L		L
28.0	L				L				L
26.0	L				L				L

A/D: Ascending/Descending series

Estimate the interval of uncertainty for this taster.

Calculate the difference threshold.

Calculate the PSE.

Based on your calculations, what would you recommend as a reasonable reduced sugar content that would be perceptually unnoticeable to the customer? Justify your answer.