Download presentation

Presentation is loading. Please wait.

Published byCaden Agers Modified over 3 years ago

1
ISO TC209 WG1, Nov. 11, 2005.Page 1 ISO TC209 WG1 N375 14644-1 Statistical Issues - reissue.ppt ISO 14644-1 Statistical Issues Mark Varney, Statistician ISO TC209 WG1 Nov. 11, 2005

2
ISO TC209 WG1, Nov. 11, 2005.Page 2 Table C.1 – Student’s t Table C.1 is correct –Confidence limit is 1-sided May wish to add an additional significant digit Add reference since different from GUM table –GUM table is 2-sided

3
ISO TC209 WG1, Nov. 11, 2005.Page 3 95% Upper Confidence Limit(UCL) Current requirement: For m = 2 to 9 locations 1.All location means must meet limit -- AND -- 2.95% UCL based on location means must meet limit

4
ISO TC209 WG1, Nov. 11, 2005.Page 4 95% Upper Confidence Limit(UCL) 1.For 5-9 locations, requirement for locations to be within limits provides 95% confidence mean is in limit. Calculation of 95% UCL is superfluous.

5
ISO TC209 WG1, Nov. 11, 2005.Page 5 95% Upper Confidence Limit(UCL) 2. “False alarm” rate of failing 95% UCL requirement when room is OK is high for 2-3 locations Example: Suppose limit calculated per section 3.2 is 1000 Room average=700, std dev=100, normal distribution m: # locations Probability of failing UCL requirement 250% 37%

6
ISO TC209 WG1, Nov. 11, 2005.Page 6 95% Upper Confidence Limit(UCL) 3.Intent of ISO 14644-1 appears to be that entire room - all locations - should be in limits 95% UCL for mean only relates to the overall room mean being within limits 4.95% UCL calculation is sensitive to outliers 5.Particulate is seldom normally distributed UCL calculation assumes normal distribution Not a critical assumption, though; method is robust

7
ISO TC209 WG1, Nov. 11, 2005.Page 7 Recommendation: Eliminate 95% UCL 1.For m=5-9, already have 95% confidence - For 4 locations, confidence is almost 95% (93.8%) 2.False alarm rate is too high for m=2-3 3.95% UCL relates to room mean; meaningful? 4.Sensitivity to outliers 5.Normality assumption often not met

8
ISO TC209 WG1, Nov. 11, 2005.Page 8 Possible Statistical Approaches Goal: Show that limits are met throughout room Suggested strategy –Sample enough locations to show with X% confidence that at least Y% of locations meet limit Statistical Approach: tolerance limits –Nonparametric –Parametric (smaller N L, but assume normality)

9
ISO TC209 WG1, Nov. 11, 2005.Page 9 Suggested Statistical Approach Select # locations to provide 90% confidence that at least 90% of locations meet limit

10
ISO TC209 WG1, Nov. 11, 2005.Page 10 Suggested Statistical Approach Tighter confidence/verification by room class

Similar presentations

Presentation is loading. Please wait....

OK

Statistical Techniques

Statistical Techniques

© 2018 SlidePlayer.com Inc.

All rights reserved.

Ads by Google

Ppt on types of business communication Ppt on web browser in java Ppt on famous indian entrepreneurs in the us Ppt on cellular technologies and security Ppt on code switching and code mixing Ppt on layer 3 switching vs layer Ppt on db2 architecture overview Ppt on automatic water level controller using microcontroller Ppt on arbitration and conciliation act 1996 Ppt on business plan example