July 2008 – Page 4 – DECISION STATS

Review-The Dark knight

The much anticipated sequel to Batman begins- and Heath Ledger’s last movie is evrything you waited for and more. Ledger makes his Joker so very own, you forget Jack ever did that at as funny man. A gaunt looking Batman battles media, politicians ,hype, mafia and Joker to the point you almost feel worried for the caped fellow.

Some references to Telecom companies used for spying, some ground zero like shots of buildings collapsed, some Chinese thugs who steal money, and you wish Hollywood escaped reality and politics. But enter the Joker and he captures the screen space to the point of overshadowing anyone else. Many a critic has predicted Oscars for best actors. Thats for you to judge as you say hello to the Dark Knight and goodbye to Heath Ledger in this most splendid action hero movie of the year. There is no Katie holmes to distract you while the otherwise perfect cast returns with Bale,Caine,Oldman and Freeman to push the franchise forward.

The action is breathtaking and unrelenting, the suspense builds up till it echoes the lovely soundtrack and Batman returns as the Dark Knight of Gotham.

Review – HanCock(y)

When Will Smith releases a movie, we all sit up and notice. Apart from the Wild Wild West, the fresh prince of Hollywood has been havings hits after enjoyable hits . Hes got a bit of Denzel looks (and a smaller bit of the acting), some of Chris Tucker motor mouth (but not too much) and some Wesley Snipes action appeal. He is the perfect leading man as of Today – with no conroversies too. And this time he comes back with an unconventional script ( I ,Robot, -I am Legend…) on a super hero who drinks too much, fumbles his timing,hits on women (!) and generally acts like a ….(Dont call him that !!!) but you need to see the movie at this point.

Charlize Theron is great as the sceptical wife of the Public Relations executive who tries to clean up the man.The move is both a spoof on action heroes and an action hero movie at the same time.Memorable scenes include a drunk and flying John Hancock (well Superman never drank !!) chasing bad guys, a super villian (!) and prison scenes. Enough said.The movie strikes you for the realistic special effects (yes it looks like he is actually flying not swinging by a rope )…and great lovely Will Smith cocky humour.

Watch the movie– its gonna be a cool cool summer and the action heroes are coming back. Bring Em On.

Cloud Computing across LAN’s ?

The concept of cloud computing is interesting and actually quite old. It lacked major backing till Google came along and is now increasingly seen as the alternative to PC (given that other alternatives like Tablet PC came and went).

This diagram and definition is from Wikipedia of course ”

Cloud computing refers to computing resources being accessed which are typically owned and operated by a third-party provider on a consolidated basis in Data Center locations. Consumers of cloud computing services purchase computing capacity on-demand and are not generally concerned with the underlying technologies used to achieve the increase in server capability. There are however increasing options for developers that allow for platform services in the cloud where developers do care about the underlying technology.”

What prevents local area networks from enforcing clouds beats me. Put all the apps and ALL the storage on the server.Since most PC OEMS insist on their standard 80 gb hard disk configuration, the IT team of a company has to work harder to enforce it, but once done – They have lower tickets to attend to. Just put thin shell ubuntu PC’s with open office on each local machine. This also makes compliance and productivity tracking much easier to do- just check the server logs. Bottlenecks of course remain that IT Compliance in companies rarely seeks to maximize business value, thus ensuring they are the first to be transferred to other teams or downsized in downturns as a cost unit not as a core unit.

You can also try Google Apps for enterprise for such initiatives. The software is now ready which wasnt the case a few years back.

More Advanced SAS Modeling Procs

A special thanks to Peter Flom ( www.peterflom.com )for suggesting the following –

5) Proc NLMIXED

PROC NLMIXED can be viewed as generalizations of the random coefficient models fit by the MIXED procedure. This generalization allows the random coefficients to enter the model nonlinearly, whereas in PROC MIXED they enter linearly. With PROC MIXED you can perform both maximum likelihood and restricted maximum likelihood (REML) estimation, whereas PROC NLMIXED only implements maximum likelihood. This is because the analog to the REML method in PROC NLMIXED would involve a high dimensional integral over all of the fixed-effects parameters, and this integral is typically not available in closed form. Finally, PROC MIXED assumes the data to be normally distributed, whereas PROC NLMIXED enables you to analyze data that are normal, binomial, or Poisson or that have any likelihood programmable with SAS statements.

http://aerg.canberra.edu.au/envirostats/bm/SASHelp/stat/chap46/sect4.htm

6) Proc Glimmix

PROC GLIMMIX fits statistical models to data with correlations or nonconstant variability and where the response is not necessarily normally distributed. These generalized linear mixed models (GLMM), like linear mixed models, assume normal (Gaussian) random effects. Conditional on these random effects, data can have any distribution in the exponential family. The binary, binomial, Poisson, and negative binomial distributions, for example, are discrete members of this family. The normal, beta, gamma, and chi-square distributions are representatives of the continuous distributions in this family.

Some PROC GLIMMIX features are:

Flexible covariance structures for random effects and correlated errors
Programmable link and variance functions
Bias-adjusted empirical covariance estimators
Univariate and multivariate low-rank smoothing
Joint modeling for multivariate data

Besides including performance enhancements and various fixes, the production release of the GLIMMIX procedure provides numerous additional features. These include:

ODS statistical graphics to display LS-means and confidence limits
Analysis of Means
Odds ratios
Custom hypotheses concerning LS-means with the LSMESTIMATE statement
New multiplicity adjustments
Beta regression

www2.sas.com/proceedings/sugi30/196-30.pdf

http://support.sas.com/rnd/app/da/glimmix.html

3) Proc QUANTREG

www.stat.uiuc.edu/~x-he/ENAR-Tutorial.pdf

Ordinary least squares regression models the relationship between one or more covariates X and the conditional mean of the response variable Y given X=x. Quantile regression extends the regression model to conditional quantiles of the response variable, such as the 90th percentile. Quantile regression is particularly useful when the rate of change in the conditional quantile, expressed by the regression coefficients, depends on the quantile. The main advantage of quantile regression over least squares regression is its flexibility for modeling data with heterogeneous conditional distributions. Data of this type occur in many fields, including biomedicine, econometrics, and ecology.

Some PROC QUANTREG features are:

Implements the simplex, interior point, and smoothing algorithms for estimation
Provides three methods to compute confidence intervals for the regression quantile parameter: sparsity, rank, and resampling.
Provides two methods to compute the covariance and correlation matrices of the estimated parameters: an asymptotic method and a bootstrap method
Provides two tests for the regression parameter estimates: the Wald test and a likelihood ratio test
Uses robust multivariate location and scale estimates for leverage point detection
Multithreaded for parallel computing when multiple processors are available

4) Proc Catmod-

http://www.uidaho.edu/ag/statprog/sas/workshops/catmod/outline.html

Categorical data with more than two factors are referred to as multi-dimensional distributions. Procedure CATMOD will be used for analyses concerning such data. PROC CATMOD may also be used to analyze one-and two-way data structures , however it is an effective means to approach more complex data structures.

PROC CATMOD utilizes a different technique to do categorical analysis than the ‘Pearson type’ chi-square. The analysis is based on a transformation of the cell probabilities. This transformation is called the response function. The exact form of the response function depends on the data type and it is normally motivated by certain theoretical considerations. SAS offers many different forms of response functions and even allows the user to specify their own, however, the most common (default) is the Generalized Logit. This function is defined as:

Generalized Logit = LOG(pi/pk),
where pi is the ith cell probability and pk is the last cell probability. The ratio of pi/pk is called an odds ratio and the log of the odds ratio is just a comparison of the ith category to the last, on a log scale. The logit can be rewritten as:
Generalized Logit = LOG(pi) – LOG(pk).
It should be noted that if there are k categories, then there will be only k-1 response functions since the kth one will be zero.

SAS Modeling Procs

Well, so you want to be a SAS Modeler. Or atleast get a job as a junior one , and then learn on the job (we all did). Here are some SAS Procs you need to brush up on-

1) Proc Reg – Continuous Regression.

2) Proc Logistic –Logistic Regression.

3) Proc Probit –Categorical regressors also included in this.

4) Proc GLM –General Linear Models based on OLS. PROC GLM handles models relating one or several continuous dependent variables to one or several independent variables. The independent variables may be either classification variables, which divide the observations into discrete groups, or continuous variables.Proc GLM is the preferred procedure for doing univariate analysis of variance , multivariate analysis of variance , and most types of regression. :Note there is a Proc Anova also.

5) Proc Mixed –The PROC MIXED was specifically designed to fit mixed effect models. It can model random and mixed effect data.PROC MIXED has three options for the method of estimation. They are: ML (Maximum Likelihood), REML (Restricted or Residual maximum likelihood, which is the default method) and MIVQUE0 (Minimum Variance Quadratic Unbiased Estimation). ML and REML are based on a maximum likelihood estimation approach. They require the assumption that the distribution of the dependent variable (error term and the random effects) is normal. ML is just the regular maximum likelihood method,that is, the parameter estimates that it produces are such values of the model parameters that maximize the likelihood function. REML method is a variant of maximum likelihood estimation; REML estimators are obtained not from maximizing the whole likelihood function, but only that part that is invariant to the fixed effects part of the linear model. In other words, if y = Xb + Zu + e, where Xb is the fixed effects part, Zu is the random effects part and e is the error term, then the REML estimates are obtained by maximizing the likelihood function of K’y, where K is a full rank matrix with columns orthogonal to the columns of the X matrix, that is, K’X = 0. I

6) Proc Genmod-PROC GENMOD uses a class statement for specifying categorical (classification) variables, so indicator variables do not have to be constructed in advance, as is the case with, for example, PROC LOGISTIC. Interactions can be fitted by specifying, for example, age*sex. The response variable or the explanatory variable can be character while PROC LOGISTIC requires explanatory variables to be numeric.

7) Proc Corr-CORR procedure computes correlation coefficients between variables. It can also produce covariances.

8) Proc Anova-PROC ANOVA handles only balanced ANOVA designs

Required reading –http://en.wikipedia.org/wiki/Regression_analysis

SAS Online Doc

Additional Reading-

http://www.pauldickman.com/teaching/sas/genmod_logistic.php

http://www.psych.yorku.ca/lab/sas/sasanova.htm

Project Management Certification (PMP)

Some resources for getting the PMP certification (based on a Linkedin Question)- This is a useful not too expensive and not very very tough certification for professionals who manage projects (and don’t we all !)

Online Websites-

Providers- http://tel.occe.ou.edu/cgi-bin/PMI_Provider/repsearch.cgi

The main website –http://www.pmi.org/Pages/default.aspx

Credentials-http://www.pmi.org/CareerDevelopment/Pages/Obtaining-Credential.aspx

Some white papers –http://www.globalknowledge.com/training/whitepaperlist.asp?pageid=502&wpcat=7&sort=&country=United+States

An additional book-http://www.amazon.com/PMP-Exam-Prep-Fifth-Passing/dp/1932735003

The main book – PMBOK