THE NRA GRADING SYSTEM  - METHOD OF CALCULATION

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Meetings used

The Meetings used for grading are signified in the annual listing produced by the NRA. If less than 4/A graders or less than 20 shooters altogether complete the course then that event is not used for grading.

Scores used
Only the aggregate scores of those eligible competitors that complete the course of fire at the meeting are counted. Central bulls-eyes are ignored. Eligible competitors are those who are affiliated members of a New Zealand Rifle Club and eligible to shoot for its teams.
At the National Championships there are three aggregates used. They are the Masefield Aggregate, the White Horse Aggregate and the Club Coffee Cup Aggregate. (These two aggregates each contain one of the scores fired at each range for the Belt). The Queens Final scores are not used. At the Marlborough Spring Meeting the aggregate of the ten ranges is divided into two aggregates - the first shoot at each range and the second shoot at each range respectively.

Adjustment for Field
To allow for the strength of the field, the number of A graders is divided by 0.45 to find the theoretical field. (Note that the number of shooters actually graded A in the most recent grading list is the number used. On some occasions B graders will enter A, which they are quite entitled to do, but they should not be counted when the adjustment is made). E.g. if 27 A graders complete an aggregate then the field is 27/0.45 = 60. If there are 90% or more A grade competitors the 10%ile position is used for the median score.

Median and 90%ile Positions
The median position is that which has an equal number of higher and lower scores i.e. the middle score - not the average. Eg. if the field is 60 then the median is the 30.5th place or the average of the 30th and 31st scores. The 90%ile position is the one that is beaten by only 10% of the field. Eg. for a field of 60 the 90%ile is the 6th place.

Ratings
The median score is allocated a rating of 1000. The 90%ile score is allocated a rating of 1040. All other scores are then rated pro-rata from these two scores.

Average Rating
The ratings achieved at each event are recorded in order. The shooter's average rating is calculated as follows: Only scores from the current season and the two previous seasons are used. (I.E. at the
beginning of each season the scores from the season 3 years previous are discarded and
there will be only 2 years of scores being used. By the end of the season there will be three
year's scores kept.)

• If a shooter has 1 or 2 ratings these are retained but no grading is given.
• If a shooter has 3, 4 or 5 ratings then the rating used is the average of these.
• If a shooter has 6, 7 or 8 ratings the lowest is discarded and the average of the rest determined.
• If a shooter has more than 8 ratings the last 8 in chronological order are used, the lowest discarded and the rest averaged.

All average ratings are rounded to one decimal point.

Grading List
The average gradings for all shooters are listed. The highest 35% receive and A grading, the next 35% a B grading and the remaining 30% a C grading.

Example
33 A grade shooters attend a Championship. The field is thus 73.3 and the median position is the 37th place. The 90%ile is the 7.3rd place.
The 37th score is 235, the 7th score 245 and the 8th 244. The median is thus 235 and is rated 1000. The 90%ile is 244.7 and rated 1040. 9.7 score points are thus worth 40 rating points. As a result the following scores are allocated the following ratings:

The shooter with 231 has ratings of 1000.0, 1008.4, 972.8, 920.7, 1021.8 and 983.5. With 6 scores the lowest (920.7) is discarded and the rest averaged to give 997.3 average rating. If the cut-off from C to B grade is at 990.2 this will give a B grade.

The shooter with 249 has ratings of 1040.0, 1032.6, 1045.3, 1023.7, 1062.0, 1023.4, 1010.2, 1054.3, 1054.2, 1038.7, 1052.8, and 1057.7. As there are twelve ratings the first 4 are discarded to give 8 and then the lowest of them (1010.2) is dropped. The average of the other 7 is 1049.0. The A grade cut-off is typically around the 1010 level and an A grading will result.

Tony Loughnan
15th January 2002