Uncertainty and Significantly Different Means - Buffer Solutions

#1
Hi there

I have discovered an "interesting" (meaning I do not know how to proceed) problem.

I am estimating an uncertainty budget for a measurement of buffer solutions. We measure the buffer solutions with two pH electrodes in the same solution at the same time. Temperature is controlled (25°C +/- 0.2). The electrodes are calibrated using primary standard buffer solutions with pH values either side of the solution being measured. Around 300 measurements are collected over 15 minutes after which the mean of the measurements of each electrode are combined to deliver the total mean, which is attributed to the pH of the buffer.

Now my problem. The method that I have just stated, I believe, is valid IF there is no significant difference between the measurements from the individual electrodes. Unfortunately, there is a significant difference.

In practical terms, the differences are small (i.e. less than the uncertainty of the primary standard buffer) but never the less statistically significant.

My question is can I use distribution of the difference between the buffers to calculate the measurement uncertainty of the electrodes or because of the statistical significance, must I go back to the drawing board and re-examine my measurement method.

Any ideas are much appreciated.
 
Elsmar Forum Sponsor
Thread starter Similar threads Forum Replies Date
R Determining Uncertainty from Gage R&R Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 0
B IEC 60601-2-10 - Accuracy of Pulse Parameters - Required Measurement Uncertainty IEC 60601 - Medical Electrical Equipment Safety Standards Series 3
F Missing value of Uncertainty B Measurement Uncertainty (MU) 8
F Issues in Uncertainty Estimation Measurement Uncertainty (MU) 5
F Operator Manual and Type B Uncertainty Measurement Uncertainty (MU) 3
F Learning Uncertainty Budget for Novice - Fluke 5520A Measurement Uncertainty (MU) 1
G Does pitch/increment/resolution of a ruled scale apply to measurement uncertainty as line item? Measurement Uncertainty (MU) 10
R Uncertainty in measurement larger than tolerance Measurement Uncertainty (MU) 2
S Uncertainty Budgets - Phase Noise (SSB), Harmonics Measurement Uncertainty (MU) 2
K ISO 17025:2017 clause 7.6.2 - Performing calibration of its own equipment shall evaluate the measurement uncertainty ISO 17025 related Discussions 6
M Informational US FDA Final Guidance – Consideration of Uncertainty in Making Benefit-Risk Determinations in Medical Device Premarket Approvals, De Novo Classificati Medical Device and FDA Regulations and Standards News 0
A Uncertainty Budget - Externally produced sensor module Measurement Uncertainty (MU) 1
E Discussion between co-worker on tolerance and uncertainty and how to apply it. Thoughts? 17025 ISO 17025 related Discussions 1
G Assigning a calibration tolerance - An x-y coordinate machine - Uncertainty as my verification tolerance General Measurement Device and Calibration Topics 4
G 3 Operator Std. Dev. and uncertainty calculation Measurement Uncertainty (MU) 2
G Reporting measurement uncertainty for custom items Measurement Uncertainty (MU) 2
L Gage R&R for test precision or uncertainty prediction? Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 2
G Uncertainty of staging a short line scale standard on longer measuring machine? Measurement Uncertainty (MU) 4
K Measurement Uncertainty Budget (MU) of for Ultrasonic Thickness gauge Measurement Uncertainty (MU) 1
G NIST SOP 29 - Assignment of Uncertainty - Question General Measurement Device and Calibration Topics 0
M Medical Device News FDA news - 05-09-18 - Draft - Uncertainty in Benefit-Risk Determinations Other US Medical Device Regulations 0
G Can Measurement Machine Bias be part of Uncertainty? General Measurement Device and Calibration Topics 1
G How to include machine error in uncertainty calculations? Measurement Uncertainty (MU) 5
D Difference between uncertainty and expanded uncertainty of measurement General Measurement Device and Calibration Topics 1
M Calibration certificates avowing accuracy beyond the uncertainty limits? Measurement Uncertainty (MU) 7
G ANAB ISO 17025 Accreditation - Uncertainty and systematic error? ISO 17025 related Discussions 6
G How many Uncertainty Measurements for Micrometers and Calipers? Measurement Uncertainty (MU) 3
G What degrees of freedom means in uncertainty budget and how do I set the value Measurement Uncertainty (MU) 2
G Uncertainty Experts - ISO 17025 - If the Distribution is Rectangular Measurement Uncertainty (MU) 2
G Uncertainty Budget Examples for Caliper, Micrometer and Dial Gauge Measurement Uncertainty (MU) 3
S Pressure Gauge Calibration Uncertainty Calibration and Metrology Software and Hardware 5
E Uncertainty of Mean - Test rig that measures water temperatures Measurement Uncertainty (MU) 3
J Internal Laboratory Scope and Measurement Uncertainty (MU) IATF 16949 - Automotive Quality Systems Standard 1
G Manual Procedure with Uncertainty Budgeting for either a Caliper or Micrometer General Measurement Device and Calibration Topics 6
C MU (Measurement Uncertainty) in an Internal Calibration Laboratory Measurement Uncertainty (MU) 1
N How to Convert Micro Volts into Temperature Uncertainty Measurement Uncertainty (MU) 1
N Include homogeneity uncertainty into budget table for thermocouples Measurement Uncertainty (MU) 1
J CMM Uncertainty Calculation Question - Deviations Measurement Uncertainty (MU) 9
M Uncertainty Budget for a Micrometer Measurement Uncertainty (MU) 5
C Uncertainty Trainer in Texas? Measurement Uncertainty (MU) 3
P Purpose of calculating Uncertainty value in calibration study Measurement Uncertainty (MU) 5
C Uncertainty Estimation for Spark Optical Emission Device Measurement Uncertainty (MU) 1
W Dimensional Measurement of 10% accuracy and 25% uncertainty standard General Measurement Device and Calibration Topics 6
B Measurement Uncertainty using Minitab Measurement Uncertainty (MU) 2
J Uncertainty budget for IR thermometry at high T - 1000 - 1500?C Measurement Uncertainty (MU) 1
N Understanding the absolute uncertainty specification for a Fluke 5500A Measurement Uncertainty (MU) 3
M Help with uncertainty calculation in the calibration of a Pyrogen Test Processor Measurement Uncertainty (MU) 7
S How to track and manage all uncertainty budgets - Database? Measurement Uncertainty (MU) 3
I UUT Accuracy as part of Uncertainty Budget Measurement Uncertainty (MU) 6
A Uncertainty Measurement - What this accuracy specification "1% + 10^5": means? General Measurement Device and Calibration Topics 2

Similar threads

Top Bottom