# The Recreational Craft Regulations 2017, Schedule 7: (Annex VII of the Directive)

Extent: E+W+S+N.I.

1.For verifying the conformity of an engine family, a sample of engines shall be taken from the series. The manufacturer shall decide the size (n) of the sample, in agreement with the notified approved body.
2.The arithmetical mean X of the results obtained from the sample shall be calculated for each regulated component of the exhaust and noise emission. The production of the series shall be deemed to conform to the requirements (‘pass decision’) if the following condition is met:
X+ k. S≤ LS is standard deviation, where:
S2=∑x− X2∕n− 1Xthe arithmetical mean of the results obtained from the sample
xthe individual results obtained from the sample
Lthe appropriate limit value
nthe number of engines in the sample
kstatistical factor depending on n (see table below)
If n ≥ 20 then k=0,860∕n.
n
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
k
0,973
0,613
0,489
0,421
0,376
0,342
0,317
0,296
0,279
0,265
0,253
0,242
0,233
0,224
0,216
0,21
0,203
0,198

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Source: https://www.legislation.gov.uk/uksi/2017/737/schedule/7 (the official version)
Page: https://openlegislation.uk/recreational-craft-regulations-2017/schedule-7
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.