June 5, 2000

The following release notes attempt to document the major changes in
each new version of SLIDA.


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The June 5, 2000 version of SLIDA. 

1. The most extensive improvement since the last version of SLIDA
has been in the documentation. Luis Escobar (who also has been
providing technical advice to this project for many years and who is
co-author of our Wiley text book that provided the technical
blueprint for SLIDA) has agreed to join me as co-author on the SLIDA
User's Manual. The SLIDA User's Manual now documents all of the
functionality in the SLIDA GUI (there remains a considerable amount
of more esoteric functionality at the command level that is less
well documented).

2. Ability to split/subset data objects (e.g., with a factor
explanatory variable comparing two or more groups) so that
individual detailed analyses can be performed more easily on the
individual groups or subsets of one's data. The "Make life data
objects for individual groups" menu item now appears in the
comparison and regression menu lists.

3. A procedure to compute the probability of successful
demonstration for a censored-data life test reliability
demonstration. The curves generated by this procedure are a
generalization of similar curves provided in Chapter 9 of Hahn and
Meeker (1991, Statistical Intervals, John Wiley & Sons) for the
normal distribution and complete data. The new procedure will
generate similar curves for lognormal, Weibull, and loglogistic
distributions for type II censored data.

4. The routines used to convert (in some cases by extrapolation)
degradation data into failure data are now more robust, allowing for
left censoring (when the degradation path is beyond the failure
definition at the first inspection) and to check for degradation paths
that seem to be going in the direction opposite from what is expected.

5. The approximate sample size determination figures allow specification
of either a censoring time or a fraction failing as input in
specifying a proposed test plan.

6. Mean time to failure is now reported when estimation output for a
single distribution or a distribution conditional on fixed levels of
explanatory variables (in a regression or accelerated test model) is
printed.

7. SLIDA was developed largely around the analysis of single
distribution data of various types with complicated censoring and
experimental regression and accelerated test data with with
relatively few test conditions and a considerable amount of
replication. In previous versions of SLIDA, methods were not
carefully tuned for regression problems with many observations, at
many different levels of explanatory variables, with little or no
replication.  A number of changes have been made to make it easier
to analyze such data. Such data sets now show up in the lists of
data objects for more procedures (By defaults that can be
overridden, SLIDA tries to identify data sets appropriate for a
particular analysis and puts them in the list of available data
objects. For example, data without explanatory variables will, by
default, not show up in lists for procedures doing regression
analysis).


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The January 21, 2000 version of SLIDA. 

1. The SLIDA User's manual is much more complete than in the past. It
is still in draft form, but contains much more useful information.

2. A few problems of compatibility with Splus2000 have been fixed.

3. When fitting a log-location-scale distribution (e.g., Weibull or
lognormal) it is now possible to fix the distribution's shape
parameter when doing ML estimation. Correspondingly, when fitting a
location-scale distribution (e.g., smallest extreme value or
normal) it is now possible to fix the distribution's scale (spread)
parameter.

4. It is now possible to generate trellis plots on repeated-measures
(degradation) data objects, making it easy to compare individual
degradation paths.

5. There are similar capabilities for making degradation residual plots.

6. Changes have been made so that the control of the axis ranges and
range over which the cdf is evaluated when plotted on probability
plots are handled consistently over the many dialog boxes that can
create such probability plots.

7. Optionally, the time/date or another specified string is placed on
the bottom right of plots. Now this is automatically suppressed in
the plots with multiple plots on one sheet.

8. Ability to edit an existing data object (e.g., to change titles, units, or
other details mapping a data frame to a life data object).

9. Ability to easily and dynamically modify a data object by editing the
associated data frame.

10. Additional example data sets have been included to illustrate the
new methods.

11. A number of users have requested access to functions used to do
bootstrapping, as described in Chapter 9 of Meeker and Escobar. Now,
file echapter09.q contains the commands used to do the examples in
that chapter. These basic tools can be used to run similar
bootstraps for other data sets. Work is being planned to extend
these capabilities to regression problems and to better integrate
with other functions and, eventually, to have bootstrap intervals as
an option from the GUI. We envision giving the user the option to do
bootstrap intervals (or likelihood-based intervals) instead of the
normal approximation intervals, if the user is willing to use the
necessary amount of computer time to compute such intervals (with
the newest generation of PCs, this now takes on the order of minutes
for small to moderate sized data sets where such improved
approximate intervals are important).

12. There is an option to include the relationship into results
object names (making it easier to keep track of such results when
fitting different models).

13. There is an option to include the response name into a repeated
measures data object (especially useful when there is a data frame
with multiple degradation readings that need to be analyzed
separately).


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The October 3, 1999 version of SLIDA.

1. Life data event plot (similar to the previously available recurrence
data event plot).

2. Option to request print out the parameter estimate
variance-covariance and correlation matrices from the GUI (it was
always available from the command level).

3. Ability to make persistent additions and changes to the
observation-type aliases (e.g., users can introduce their own word
or words to indicate which observations are censored and which are
failures, extending the build-in list).

4. Better control over SLIDA default options (e.g., confidence
level, number of digits in tables, and whether the response should
be plotted on the x axis or the yaxis, list of quantiles used in
estimation, names for censoring indicators), including the ability
to make global changes to some options and, if desired, to save such
changes across sessions.

5. More consistency in how defaults are changed across GUI dialog
boxes.

6. Ability to see a perspective or contour plot of the likelihood
function for location-scale and log-location-scale distributions.

7. Ability to compare likelihood contours for location-scale and
log-location-scale distributions when comparing samples from
different populations or processes.

8. Option to mark each plot with time and date and/or name.

9. An alternative color scheme has been chosen and this one works
much better for SLIDA graphics. In addition, as explained in the
user manual, there is an option to have all graphics come out as
pure black and white (no grey scale). These options (requested by
several users) avoid the "washed-out" look that some graphics had in
the past when multiple colors were used on one plot.

10. SLIDA seems to work fine on the latest version Splus2000.
However, because Splus4.5 and Splus2000 have different menu
structures, it is necessary for me to post different versions of
SLIDA for the two different versions. I have now done this.

Also the documentation has been extended and the graphics in this
document are now black and white so that they print much better on
a laser printer. Additionally, I have figured out how to make the
pdf using 3.0 compatibility mode in Adobe Acrobat, but I still
recommend downloading the latest free version of Acrobat Reader
from www.adobe.com.



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The April 24, 1999 version of SLIDA.

1. Six-distribution probability plots,

2. Ability to present the response on the y-axis in life versus stress
plots,

3. Regression diagnostics (especially residual plots) 

4. Sensitivity analysis procedures