How should I use the Grouped Data Settings in
data settings in
Weibull++ affect how the unreliability
estimates are plotted on the probability plot. These
settings are available only when working with grouped
When using rank regression with grouped
data, the software will plot only the data points that
correspond to the highest median rank position in each
group. For example, consider two groups of data with 10
units each. By default, the software will plot only two data points:
the 10th rank position out of 20, and the 20th rank
position out of 20. The regression line is then fitted
to the two points. When you select the Ungroup on
Regression option, the software will plot each
individual data point in the group. The regression line
is then fitted to all the data points. In general,
grouped data analysis provides parameter estimates that
have wider confidence bounds, while ungrouped data
analysis provides parameter estimates with much narrower
When using MLE analysis, the
plotted line is independent of whether data points are
treated as grouped or ungrouped data. The option to
Ungroup on MLE Plot is only for changing the way the
data points are displayed on the MLE probability plot.
Note: When working with grouped failure
data, you have to be cautious about ungrouping the data.
In grouped data, it is assumed that the
failures occur at some time in the interval between the
previous and the current time-to-failure. For example, for a group of 10 units with a failure time of 100 the software will assume that the 10 units failed between 0 and 100 hours. If you select the option to Ungroup on
Regression, the software will treat the 10 units as
failures that occur at exactly 100 hours.
How can I customize the way Xfmea/RCM++ prioritizes and
highlights failure causes listed in my FMEA?
In order to highlight the most
serious issues in the design you’re analyzing,
Highlight Priority feature in
Xfmea/RCM++ allows you to color-code the
failure causes listed in your FMEA. By default, when the
Highlight Priority feature is enabled, the software uses a
simple risk ranking logic to assign failure causes to
three priority levels (which are named "Low," "Medium"
and "High," and color-coded in green, yellow and red,
respectively). This simple logic allows you to set the
thresholds for each level based on any one of the risk
priority metrics (e.g., RPN, Severity, etc.) that are
enabled for the project.
As an alternative, you
can use the Risk Ranking feature (available in
Version 5.0.1 or higher) to customize the number of
priority levels, as well as their associated names and
colors. This feature also allows you to define a more
complex ranking logic that considers multiple metrics
rather than, say, RPN alone. This configurable logic can
be saved in the active library so it will be easy to
apply to any particular analysis project.
save customized priority levels and their associated
risk ranking logic in the active library, open the
Profiles/Libraries Manager and select an interface style
that will include your customized logic. In the Edit
Interface Style window, click RPNs under the Risk
Assessment heading in the navigation panel. Then, in the
Highlight Priority Based on area, choose Risk Ranking
from the drop-down list and click the Risk Ranking Logic
window that appears, click the icon inside the Priority
column heading to open the tool for defining priority
To create a new priority level, enter the appropriate
information into an empty row. (Xfmea will always
include an empty row for defining new priority levels.
If you delete the empty row, it will reappear when you
close and reopen the window.) Return to the Risk Ranking window when you are finished
defining your priority levels.
Every row in the
Risk Ranking window represents a rule for assigning
causes to priority levels. If a cause satisfies all the
criteria in a row, it will be assigned the priority
level displayed at the end of that row, and it will be
color-coded with whatever color you selected for that
priority level. You can define up to three criteria for
each rule, and each criterion has three columns. The
first column specifies a rating or metric while the
third column specifies a numerical value. The middle
column specifies whether the rating/metric must be equal
to (=), greater than (>), less than (<), greater than or
equal to (>=) or less than or equal to (<=) the
specified numerical value.
As an example,
suppose you decided to include the following risk
ranking logic in your interface style.
A failure cause has a CRITICAL priority level if its
severity rating is 9 or higher AND its RPN is 300 or
A failure cause has a HIGH priority level if its
severity rating is 6 or higher OR its RPN is greater
A failure cause has a MEDIUM priority level if its
severity rating is greater than 3 OR its RPN is 100 or
All other failure causes have a LOW priority level.
You would configure the Risk Ranking window as shown
Note: The first
rules in the table are given priority over later rules.
So, for example, if a cause has a severity rating of 10
and an RPN of 800, then it will be marked critical
rather than high priority, even though it also satisfies
the criteria for high priority.
this interface style, you can apply it to any particular
analysis project. To turn the Highlight Priority feature
on or off while you’re working with the analysis data,
choose FMEA > Highlight Priority or click the
Highlight Priority feature is turned on, the failure
causes will be color-coded according to the ranking
logic defined in your interface style. The color-coding
will appear in the worksheet and hierarchy views of your
FMEA, and it will also appear in the filtered view when
filtered by causes.