A Screening Tool for Selection of Field Odor Assessors

Figures & data

Figure 1. Gender, age, and residence distributions of the tested population. (A) Age and gender distributions. (B) Residence distribution of women. (C) Residence distribution of men. The total number of individuals was 179. Age and residence were evenly distributed between women and men except for the age group 61–70.

Table 1. Grading procedure in each part of the odor test

Part 1	Forced choice: 8 points for each correct answer (5 sets). Maximum: 40 points.
Part 2A	Odor intensity: 30 points for correct answer. 8 points are deducted for one-place position error, 16 points for two-place error, etc. Maximum: 30 points.
Part 2B	Odor intensity: The average rating of each n-butanol concentration by the tested population (179 individuals) is determined first. Then, for every individual, the distances of all ratings from the average are summed over all solutions. The final grading is as follows: 12 points are given if the sum of these distances is in the range 0–2.5; 11 points for 2.5–5; 9 points for 5–7.5; 6 points for 7.5–10; and 2 points for 10-12.5. Maximum: 12 points (an example is shown in Table 2).
Part 3A	Hedonic tone: The average ratings of the two selected n-butanol solutions by the tested population (179 individuals) are determined first. Then, for every individual, the distances of ratings for these two solutions from the average are summed. The final grading is as follows: 7 points are given if the sum of the two distances is in the range 0–2.5; 6 points for 2.5–5; 4 points for 5–7.5; and 1 point for 7.5–10. Maximum: 7 points.
Part 3B(I)	Hedonic tone: The average rating of each odor type by the tested population (179 individuals) is determined first. Then, for every individual, the distances of ratings for each solution from the average are summed. The final grading is as follows: 7 points are given if the sum of distances is in the range 0–2.5; 6 points for 2.5–5; 4 points for 5–7.5; and 1 point for 7.5–10. Maximum: 7 points.
Part 3B(II)	Odor character: The description of every solution most frequently selected by the tested population (179 individuals) is determined first. For each individual, 1 point is given if he or she uses one of the most frequently used descriptions of each solution; 0.5 point if he or she uses one of the less frequently used descriptions; and no point if he or she uses a rarely used description. Maximum: 4 points (1 point for each solution).
Total	Maximum: 100 points

Table 2. An example of the calculations used in part 2B of the odor test to determine a grading based on “average odor perception.”

Bottle No.	1	2	3	4	5	6	7	8	9	10
Candidate's evaluation (0–6 scale)	0	0	1	2	3	4	5	5	6	6
Average of the population	0.62	1.07	1.59	1.98	2.68	3.20	3.85	4.42	5.01	5.47
Distance from average (absolute values)	0.62	1.07	0.59	0.02	0.32	0.80	1.15	0.58	0.99	0.53
Sum of distances = 6.66
Notes: In this example, because the sum of distances appeared to be 6.66, this candidate received 9 points out of 12, as detailed in Table 1.

Figure 2. Test results for all 179 individuals. (A) Part 1: Triangular forced choice—percentage of correct answers given for each set (maximum: 40 points). (B) Part 2A: Odor intensity—replacing 1 of the 10 bottles previously removed from a 10-point static scale of n-butanol, scored according to the distance from the correct position (maximum: 30 points). (C) Part 2B: Odor intensity—describing intensity of n-butanol samples comprising a 10-point static scale (maximum: 12 points). (D) Part 3A: Hedonic tone descriptions of two n-butanol samples—two bottles selected for each individual, previously described by the individual as “weak” and “strong”, respectively (maximum: 7 points). (E) Part 3B(I): Hedonic tone descriptions of four different solutions (maximum: 7 points). (F) Part 3B(II): Odor character—three descriptors most frequently given to d-limonene, butanoic acid, p-cresol, and n-butanol (maximum: 4 points).

Figure 3. Final scores of all 179 candidates in ascending order. The median (87.50 points) and the 25th percentile (80.75 points) are marked.

Figure 4. Percentages of candidates who passed the test (i.e., fell within the top 75%), according to gender (A), residence (B), and age (C).

Figure 5. Impacts of the two main parts of the test on the final score and on the percentage of candidates who passed the test (i.e., who fell within the top 75%). (A and B) Parts 1+2A (based on a candidate's ability to distinguish between different odor types and various odor intensities). (C and D) Parts 2B+3 (based on a candidate's deviation from the “average odor perception” of the tested population).

Figure 6. The differences, in ascending order, between the scores (% of maximum) obtained in parts 1+2A and parts 2B+3. The median indicates that half of the candidates had a difference above or below 13.6, whereas the upper 5% had a difference of over 40. The latter candidates are potentially hypersensitive; they performed excellently in the first part of test (based on ability to distinguish between different odor types and different odor intensities), but relatively poorly in the second part of the test (based on deviation from the “average odor perception” of the tested population).

Figure 7. Percentages of individuals who rated odor intensity as at least “strong” for each of the bottles in the n-butanol static scale (part 2B).