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  The Rating System        
  Sample dispatch | Evaluation of results | Rating system | Reporting | Annexes | Test Rounds
 
 
The Rating System

The laboratory is given an in-round rating for every particular test meaning that the laboratory is given an in-round rating for germination, for purity, for OSD, for moisture, and for tetrazolium testing. In addition, each test has an overall rating derived from the performance over six rounds. A laboratory may have an overall A for germination but an overall BMP  for OSD for instance.

The In-Round Rating for Purity, Germination, Moisture, and Tetrazolium

The in-round rating system for purity, germination, moisture, and tetrazolium is based on the sum of absolute Z-scores. Only normal seedlings and pure seeds are taken into consideration for germination and purity. Z-scores for abnormal seedlings and ungerminated seeds are also reported but do not affect the in-round rating. A, B, C and BMP ratings are given. The in-round rating system for these tests is shown in Table 1.

Table 1: In-round rating system for purity, germination, moisture, and tetrazolium


The In-Round Rating for Other Seed Determination

The performance in OSD is reported as a percentage of retrieved and identified seeds to genus level of seeds added to a round's sample. Identification to species level is expected. The species names must be reported in accordance with the current version of the ISTA List of Stabilized Plant Names. Synonyms will not be accepted. Samples sent to the participants have not been purified before adding the other seed inclusions. Therefore, seeds other than those that were added can also be found but they are not considered in the rating.
The in-round rating is based on the actual retrieval rate of a distinct species. The percentage of retrieved seeds for each species among all participants is calculated (Table 2). Based on the actual retrieval rate, a factor is assigned to each added species to take the relative difficulty into account. This factor is multiplied by the total number of seeds added for this species. Then the factor is multiplied by the number of seeds found by the laboratory. The percentage of retrieved and identified seeds determine the in-round rating.
The thresholds for assigning a factor are given in Table 2.

Table 2: Thresholds defining the factor assigned to each species based on the actual retrieval rate of all seeds added of a distinct species
 
The thresholds for the OSD ratings are given in Table 3.

Table 3: In-round rating for OSD based on retrieval and identification rate
 
An example for this rating system is presented in Table 4.

Table 4: Example laboratory results (Test round 04-1 B.nap, Brassica napus)
* The retrieval rate [%] is the mean for all participants
 
The Overall Rating

The determination of the overall rating is the same for all tests to have a uniform system that can be applied for all tests once the in-round rating system is defined. Numerical values are attributed to the different in-round ratings. The values are then added for each test over the last six rounds as given in Table 5.

Table 5: Overall rating for all tests based on the in-round ratings over the last six rounds
 
 
Last update: 06.11.2007

 


Latest issue of Seed Testing International Issue 156



STI 156 October 2018
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