Regression for MTBF (Medical Device: Repairs vs Install Base) with Reliability Data

Romvill2002

Involved In Discussions
#11
Re: Regression for MTBF (Medical Device: Repairs vs Install Base) with Reliability Da

Hi Bev,
Sorry I forgot to mention that the service data is a number of defects that needs repairs not number of defective devices. Is P-chart still good? or U-chart? Thanks again
 
Elsmar Forum Sponsor

Bev D

Heretical Statistician
Staff member
Super Moderator
#12
Re: Regression for MTBF (Medical Device: Repairs vs Install Base) with Reliability Da

It depends. at low defect rates the binomial and the Poisson converge so if you typically get only one defect per instrument then either will work. but if your defect rate is high then the u chart is better - the only way to know is try. you might also plot out the distribution of defects per instrument to see if many defects cluster on a few instruments. that will help determine which chart is better
 

Romvill2002

Involved In Discussions
#13
Re: Regression for MTBF (Medical Device: Repairs vs Install Base) with Reliability Da

Majority of our devices come in with average 3-4 defects per unit. If I treat each defect as units then I'm cool to use P-chart.
 

Bev D

Heretical Statistician
Staff member
Super Moderator
#14
Re: Regression for MTBF (Medical Device: Repairs vs Install Base) with Reliability Da

in that case you are better off starting with a u chart...
At that rate there is definitely a difference between the p chart and the u chart. use the u chart...number of defects divided by install base.
 

Bev D

Heretical Statistician
Staff member
Super Moderator
#16
Re: Regression for MTBF (Medical Device: Repairs vs Install Base) with Reliability Da

I know this sounds counterintuitive but to get the average pbar you do accumulate (or sum) the install base of all of the months. This yields a large number and you are counting the same instruments many times, BUT you need to think about the instruments as 'independent' opportunities each month...from a physics standpoint they aren't but by plotting the failure rate per month, you are treating them as if they are. and if you really think about it you are using the number of devices as opportunities and there is more to the opportunity than just the device. This is what we do for our instruments and the bottom line is that it works.

the better way is to use the number of uses in a month as the area of opportunity (which we are beginning to do) but this data is not easy to get. so many people use number of devices as a surrogate...
 

Romvill2002

Involved In Discussions
#17
Re: Regression for MTBF (Medical Device: Repairs vs Install Base) with Reliability Da

Hi Steve,

Thanks for the advice. You are definitely correct. The number of uses per month would be ideal but very difficult to gather. We are now starting to design method to track down number of uses for newer devices but will ll the product mixes pure data will take a while to achieve in the field. But anyway atleast we have p-chart to start finding process variation and trends.

Thanks gain!!!
 
Thread starter Similar threads Forum Replies Date
M Problem with nonlinear regression Using Minitab Software 12
V Regression and homoscadasticity test Statistical Analysis Tools, Techniques and SPC 8
S Significance of regression, correlation coefficient, hypothesesi, confidence interval Using Minitab Software 8
S Least squares estimate, regression model and corresponding residuals Using Minitab Software 13
N Regression Model (Minitab 18) - Which values my input parameters should have Using Minitab Software 2
A Why I get a different kind of regression equation when I do the same data in a differ Using Minitab Software 7
P Basic Minitab Help - It's about Linear Regression Using Minitab Software 1
S Regression Control Chart - Process Capability Statistical Analysis Tools, Techniques and SPC 18
C Regression with Life Data, Incorrect Minitab Documentation? Reliability Analysis - Predictions, Testing and Standards 4
P How to do Multiple Regression Analysis in Minitab 16 Using Minitab Software 8
B Using Minitab 17's Stepwise Regression to Predict Feature Using Minitab Software 2
A Predictive Model Development (Regression?) Statistical Analysis Tools, Techniques and SPC 5
S How to use Dummy Variable in Regression Model in Minitab Six Sigma 2
S ANOVA/Regression - Analyzing a Dataset which contains over 4500 Points Using Minitab Software 3
O Minitab Script to Save Regression Plots to an Image File Using Minitab Software 8
W Zero setting of correlation graph when plotting best fit linear regression Statistical Analysis Tools, Techniques and SPC 7
S Regression Analysis / ANOVA using Excel Excel .xls Spreadsheet Templates and Tools 2
E How to run an OLS or Logistic Regression when I have Panel Data in Minitab Using Minitab Software 1
S Using Minitab for Multinomial Logistic Regression Using Minitab Software 2
J Minitab Rank Deficiency Issue - Binary Logisitic Regression Using Minitab Software 1
M Understanding of Regression and ANOVA in Minitab Statistical Analysis Tools, Techniques and SPC 8
P Regression Analysis for Aging Study in Minitab Statistical Analysis Tools, Techniques and SPC 10
A Questions about Regression for Modeling, Best Experimental Design Using Minitab Software 2
N Linear Regression Formula with Four Variables to a Power Regression Formula Using Minitab Software 2
Q Regression Analysis for the Attached Data - help needed - TIA Reliability Analysis - Predictions, Testing and Standards 13
B Regression analysis with discrete dependent variable and continuous independent var. Statistical Analysis Tools, Techniques and SPC 13
S How to interpret a Linear Regression in Minitab? Using Minitab Software 3
D Multiple regression with student t distribution Using Minitab Software 1
P How to do Nonlinear Regression and generate a Correlation Statistical Analysis Tools, Techniques and SPC 14
BradM Calling all Regression Analysis Pros! Statistical Analysis Tools, Techniques and SPC 1
C Degrees of Freedom with Linear Regression - Pressure Sensor Uncertainty Measurement Uncertainty (MU) 15
S CQE sample exam - Question 23 about a regression model Statistical Analysis Tools, Techniques and SPC 3
R Prediction Intervals for Quadratic Regression Statistical Analysis Tools, Techniques and SPC 4
S Interpreting Linear Regression Results from Minitab Using Minitab Software 15
R Can Factorial Design provide Regression Equation like RSM? Using Minitab Software 4
V Identifying Significant Factors - Regression Analysis vs Correlation vs ANOVA vs DOE Quality Tools, Improvement and Analysis 7
Q Can I use Regression Analysis in the following scenario Statistical Analysis Tools, Techniques and SPC 18
E Minitab Regression Analysis to predict Horse Racing result Using Minitab Software 2
J Binary logistic regression for attribute/discrete data Using Minitab Software 7
M Regression Analysis Help - Factors influencing a Dependent Variable Using Minitab Software 7
N Using Regression Analysis in Excel - Predicting a Value Statistical Analysis Tools, Techniques and SPC 30
W Z-values in Logistic Regression stem from a Wald test? Using Minitab Software 7
W Discrete vs. Continuous Variables and Linear Regression. Statistical Analysis Tools, Techniques and SPC 7
S How to represent interactions in non-linear regression analysis in Minitab Using Minitab Software 5
J Non-Normally Distributed Residuals - Regression to determine how many testers I need Using Minitab Software 13
I Partial Least Square Regression Result - Question Using Minitab Software 3
J Regression Equations - Can you move terms around I.E. simple algebra? Using Minitab Software 4
A Binary Logistic Regression - Evaluation of Survey Responses Quality Tools, Improvement and Analysis 5
J Evaluating a Regression Model Using the Constant Variance Assumption Six Sigma 8
T Value of Regression Analysis in a plastic injection molding atmosphere Statistical Analysis Tools, Techniques and SPC 4

Similar threads

Top Bottom