Colorado-Wyoming Chapter

Volume 33, Number 1

Spring Meeting - April 5, 2002

National Center for Atmospheric Research                                
Table Mesa Road                                                 
Boulder, Colorado  

(The following schedule was updated March 20, 2002)                                                    

9:00 Registration and informal chats (coffee/tea/muffins/rolls)

9:15 Election of New Officers

Pres-Elect

Newsletter Editor

9:30 Presentation of Maurice Davies Awards

9:35 Presentation of Outstanding High School AP Statistics Students Awards

9:45 Major Scott Frickenstein, USAF Academy

"Estimating Optimal Age Replacement Policies"

Abstract: We develop and estimate optimal age replacement policies for devices whose age is measured in two time scales. For example, the age of a jet
engine can be measured in the number of flight hours and the number of landings. Under a single-scale age replacement policy, a device is replaced at age t or
upon failure, whichever occurs first. We show that a natural generalization to two scales is to replace non-failed devices when their usage path crosses the
boundary of a two-dimensional region M, where M is a lower set with respect to the matrix partial order. For lifetimes measured in two scales, we consider
devices that age along linear usage paths. We generalize the single-scale long-run average cost, estimate optimal two-scale policies and give an example. We
note that these policies are strongly consistent estimators of the true optimal policies under mild conditions, and study small-sample behavior using simulation.

10:30 Jim Luhring and Johanna Lewis, Cherry Creek High School

" Trout Streams, Slot Limits, and A Generalized Geometric Probability Distribution"

Abstract: High school Advanced Placement statistics students were invited to solve a wait-time simulation problem on the Free Response part of the 1998 AP
Statistics Exam. A natural extension for this problem was to modify the geometric probability distribution for the second success on the nth trial, then
generalize to the kth success on the nth trial. Students were asked to investigate this through tactile simulation, technical simulation, theory, and
experimentation. Once these distributions were confirmed, the students were required to apply the expected value to solve the original problem.

11:00 Lunch

1:00 Tressa Fowler, University of Colorado- Denver

"Bootstrap Conficence Intervals for the Binomial Parameter: How Good is Their Coverage When the Sample Size is a Poisson Random Variable"

Abstract: Certain measures of forecast quality (e.g. probability of detection) are essentially binomial probabilities. However, lack of systematic observations for
forecasts may cause forecast/observation data to violate the assumptions of the binomial model. In these cases, not only are the numbers of successes
random, so are the numbers of observations.

Interval estimates of measures of forecast quality are more useful than point estimates for comparing different forecasts. Traditional interval estimates based on
the binomial distribution may underestimate the true variability in the forecast/observation data, yielding a narrower interval than appropriate. This additional
variability can be addressed through the use of conditional models, propagation of error formulas, and computer resampling methods. Interval estimates based
on these methods are computed and compared for simulated data where the conditional distribution of the number of successes X given the sample size N is
binomial and the sample size $N$ is distributed as Poisson. Simulated data include both large and small samples.

Additionally, counts of observations may not fit the Poisson model well. The parameter of the Poisson distribution may vary with the weather conditions,
seasons, availability of observers, etc. This may cause counts of observations of weather hazards to appear to be over dispersed. Using the same methods,
interval estimates are constructed using a second set of simulated data similar to the first, but with over dispersed Poisson counts.

Single simulations of the intervals for each set of data are compared to each other. Additionally, the correlation between X and N is estimated and the effect of
this correlation on the intervals is discussed. Finally, the nominal coverage of each method is estimated via multiple simulations.

1:45 Adjourn

2:00 Organizational/Planning Meeting for New Officers

Registration: $5

Open Letter to the Members from the Chapter President

Greetings and Farewell,

As I draw to the end of my tenure as Chapter President I want to take this opportunity to thank all for you for the support you have given to the chapter activities and to me personally over the last year.  Next month Dr. Jim Luhring, the President-Elect, will take the helm for the next year and I wish him all the best in the months to come.  It has been a challenging and rewarding experience for me and I'm sure he will find it just as enjoyable and satisfying. 

Jim has taken the initiative in organizing the Winter Workshop for AP Statistics teachers throughout the Colorado-Wyoming area for the last three years and, as you will read elsewhere in this newsletter, the programs have been a resounding success for those who have had the opportunity to participate.  The workshops represent ASA and the chapter's contribution to fostering statistical interest among high school students by giving their teachers the best tools to help them prepare both for our industrial technical world and the quantitative coursework they will encounter as they progress through their future
undergraduate curricula.  Well done, Jim!

I would also like to extend my special thanks to Dr. Karen Kafadar of the University of Colorado at Denver for her outstanding service as Council of Chapters Representative both before and during my tenure and most especially for the wonderful symposium in memory of John W. Tukey that she conceived and almost single-handedly organized last Fall.  That event has to rank as the highlight of my experience with the chapter over the last thirteen years.

The other officers with whom I have served have been very helpful to me and I would be remiss if I did not single them out for individual thanks.  Jack Powers has been a rock of dependability and service "above and beyond" as the Chapter Secretary.  Dr. Bill Navidi and Dr. Craig Williamson not only carefully maintained the Chapter's accounts during their terms as Treasurer, they have also been a source of unfailingly good advice and counsel.  Jim Talboy labored long and diligently in researching and compiling information for the newsletters as Editor.  Jim zumBrunnen has been the finest and most proactive Webmaster that one could hope for.   My sincere thanks to you all.

That brings me to a pressing item of business for the chapter:  Election of new officers.  Karen is at the end of her regular term as COC Representative and Jack's term as Secretary is also drawing to a close. Both have volunteered to stay on in their current positions for at least the next year and I recommend that we accept the offers by acclamation at the Spring Meeting.  Jim Talboy is ending his time as Newsletter Editor and, of course, a new President-Elect has to be chosen to succeed Jim Luhring as he moves up to President.  Thus, we have at least two offices to fill for the next couple of years.  I have had the good fortune to have held three chapter offices (well, two-plus since President-Elect and President automatically go together) at different times since 1989.  These have been both challenging and professionally rewarding to me.  I would like to encourage others to help build and maintain the chapter in the coming months by volunteering to fill one of these impending vacancies.  The Chapter membership will elect the new officers at the Spring meeting next month and they will take up the Chapter business at its conclusion.  Serving as a chapter officer is a way to have a primary influence on the direction we take for the future so, if you have some ideas you would like to see adopted, please come and join the executive board in working to get them implemented.  You can express your interest in any of the opening positions by giving a note, e-mail, or phone call to Jack Powers or Jim Luhring at the contact points shown on the web site or the return address of the newsletter.   I offer my sincere thanks in advance for your support to the chapter.

The last point I would like to address is my desire to see more personal news items about chapter members for the newsletter.  Obviously this cannot happen unless you, the general members, let us know what you are doing and publishing.   I love to hear of professional recognition, publication, advancement, and re-affiliations for other members of the Colorado-Wyoming statistical community.  So I encourage you to drop an electronic or written line to the Secretary or newsletter editor when you have a success to share.  We are a professional community and we all celebrate when any one of us can celebrate.

Once again, thank you all for your support and you have my best wishes for your future success as I stand down and say farewell.

Tom Gatliffe

Karen Kafadar Received ASQ's Hunter Award

Karen Kafadar was presented with the 2001 William G. Hunter Award at the Fall Technical Conference in Toronto, Canada.   The Statistics Division of the American Society for Quality established the award to recognize outstanding accomplishments in the field of applied statistics.  Karen is a professor of statistics at CU-Denver and the CO-Wy Chapter Representative. 

Winter Workshop A Success

The third "Stats Anyone?" workshop was held at Cherry Creek High School on Saturday, Feb. 9, 2002.    The event was a one day workshop on teaching statistics at the high school level, geared for high school Advanced Placement statistics teachers.  The workshop was sponsored by Colorado-Wyoming Chapter of the ASA, Cherry Creek School District, and Cherry Creek High School. Twenty participants attended this year's workshop.

Tom Gatliffe, CO WY ASA President announced to the group that the local chapter would like to give award certificates to the outstanding high school AP statistics students at their various schools.  The winners of these awards will be announced at the Spring Meeting.

Presentations were given by Amy Biesterfeld from the University of Colorado-Boulder, Sharon Bruce from Colorado Christian HS, and John Dover from Overland HS.  Karen Kafadar,   introduced Jessica Utts from the University of California - Davis.  Jessica is the chairperson of the AP Statistics Test Development Committee.  Jessica began by answering
questions about the AP Statistics syllabus, the  examination given in May, and the changes in the AP Statistics curriculum.  She then gave a presentation about ESP (extra sensory perception) experiments and how they are analyzed.

Jim Luhring thanks all those who helped him organize this event.

Chapter Notices