DSpace Collection:
http://dspace.library.iitb.ac.in/jspui/handle/100/13803
2015-03-03T03:17:31ZOn optimal two-level supersaturated designs
http://dspace.library.iitb.ac.in/jspui/handle/100/17349
Title: On optimal two-level supersaturated designs
Authors: Singh, Rakhi; Das, Ashish
Abstract: A popular measure to assess two-level supersaturated designs is the $E(s^2)$ criteria. Recently, Jones and Majumdar (2014) introduced the $\mbox{{\it UE}}(s^2)$ criteria and obtained optimal designs under the criteria. Effect-sparsity principle states that only a very small proportion of the factors have effects that are large. These factors with large effects are called {\it active} factors. Therefore, the basis of using a supersaturated design is the inherent assumption that there are very few active factors which one has to identify. Though there are only a few active factors, it is not known a priori what these active factors are. The identification of the active factors, say $k$ in number, is based on model building regression diagnostics (e.g. forward selection method) wherein one has to desirably use a supersaturated design which on an average estimates the model parameters optimally during the sequential introduction of factors in the model building process. Accordingly, to overcome possible lacuna on existing criteria of measuring the goodness of a supersaturated design, we meaningfully define the $ave(s^2_k)$ and $ave(s^2)_\rho$ criteria, where $\rho$ is the maximum number of active factors. We obtain superior $\mbox{{\it UE}}(s^2)$-optimal designs in ${\cal D}_U(m,n)$ and compare them against $E(s^2)$-optimal designs under the more meaningful criteria of $ave(s^2_k)$ and $ave(s^2)_\rho$. It is seen that $E(s^2)$-optimal designs perform fairly well or better even against superior $\mbox{{\it UE}}(s^2)$-optimal designs with respect to $ave(s^2_k)$ and $ave_d(s^2)_\rho$ criteria.2015-02-04T00:00:00ZD- and MS-optimal 2-Level Choice Designs for $N\not\equiv 0$ (mod 4)
http://dspace.library.iitb.ac.in/jspui/handle/100/16234
Title: D- and MS-optimal 2-Level Choice Designs for $N\not\equiv 0$ (mod 4)
Authors: Singh, Rakhi; Chai, Feng-Shun; Das, Ashish
Abstract: Street and Burgess (2007) present a comprehensive exposition of designs for choice experiments till then. Our focus is on choice experiments with two-level factors and a main effects model. We consider designs for choice experiment involving $k$ attributes (factors) and all choice sets are of size $m$. We derive a simple form of the Information matrix of a choice design for estimating the factorial effects. For $N$ being the number of choice sets in the design, we obtain $D$- and $MS$-optimal designs in the class of all designs with given $N$, $k$ and $m=2$. For given $N$ and $k$, we show that in many situations $D$-optimal designs for $m=2$ are superior than the optimal design for $m=3$ and $m=5$. Also, $MS$-optimal designs with $m=2$ are always better than the best designs under the same optimality criteria for any odd $m$. Furthermore, with respect to $trace$-optimality, there is no optimal design for $m>2$ which is better than the optimal design for $m=2$.2014-11-22T00:00:00ZCharacterization and Optimal Designs for Choice Experiments
http://dspace.library.iitb.ac.in/jspui/handle/100/16233
Title: Characterization and Optimal Designs for Choice Experiments
Authors: CHAI, FENG-SHUN; DAS, ASHISH; MANNA, SOUMEN
Abstract: Street and Burgess (2007) present a comprehensive exposition of designs for choice experiments till then. The choice design involves $n$ attributes (factors) with $i$-th attribute at $l_i$ level, and all choice sets are of size $m$. A choice design comprises $N$ such choice sets. Recently, Demirkale, Donovan and Street (2013) considered the setup of symmetric factorials ($l_i=l$) and obtained $D$-optimal choice designs under main effects model. They provide some sufficient conditions for a designs to be $D$-optimal. In this paper, we first derive a slightly modified Information matrix of a choice design for estimating the factorial effects of a $l_1 \times l_2 \times \cdots \times l_n$ choice experiment. It is seen that such a modification gives the Information matrix the desired additive property and thus, overcomes the existing shortcoming of situations where, with addition of a choice set the information content of the design decreases. While comparing designs with different $N$, we see that one needs to work with the modified information matrix. For a $2^n$ choice experiment, under the main effects model, we give a simple necessary and sufficient condition for the Information matrix to be diagonal. Furthermore, we characterize the structure of the choice sets which gives maximum $trace$ of the Information matrix. Our characterization of such an Information matrix facilitates construction of universally optimal designs with minimal number of choice sets and gives more flexibility for choosing $m$. Finally, we provide universally optimal choice designs for estimating main effects, which are optimal in the class of all designs with given $N$, $n$ and $m$.2014-11-21T00:00:00ZA Myth called ‘Any Branch Banking’ - Service Charge Discrimination : Misrepresentation of Monetary Policy Regulatory Stance
http://dspace.library.iitb.ac.in/jspui/handle/100/16232
Title: A Myth called ‘Any Branch Banking’ - Service Charge Discrimination : Misrepresentation of Monetary Policy Regulatory Stance
Authors: Das, Ashish
Abstract: The term “Inter-sol charges” has been used frequently by banks and off late by Reserve Bank of India (RBI). The word ‘sol’ means branch. Thus intersol charges mean inter-branch charges. These are charges levied by banks for using service of branches other than the home branch where a customer originally opened his account. With prevalence of core banking solution (CBS), when a customer opens an account at a bank branch, he becomes a customer of the bank and not of the branch. In the CBS environment, the account resides in a central server at a location different from where it is opened. Though it is superficially ‘tagged’ to the parent or home branch it can be operated from any branch of the bank with equal ease. In fact, if CBS is not functioning, no transaction can be carried out in the account either in the parent branch or any other branch. This is the concept of ‘Any Branch Banking’. However, banks on lines similar to toll imposed on newly constructed bridges / roads, devised means to charge toll by interpreting intersol charges as charges for using CBS to get a service at a non-home branch, thereby attempting to rationally differentiate charges at home and non-home locations for a banking service. Incidentally, banks never reasoned (and rightly so) intersol charges as attributable to handling charges– be it, non-home cash handling; non-home cheque handling; non-home passbook handling; non-home customer handling, etc.
RBI through its July 1, 2013 notification directed banks not to impose any intersol charges (or toll). However, the same notification suggested that banks can impose a peculiar toll in the name of cash handling charge (when customers deposit cash into or withdraw cash out of their bank accounts, even if amount involved is small) at a non-home branch while equivalent charges do not exist at the home branch. Getting a cue from the notification, State Bank of India now charges their customers Rs. 50 for every non-home cash deposit, even when the deposit amount is small (say, in the range of Rs. 10 to Rs. 1000). Thus the RBI notification has induced banks to introduce intersol charges for cash handling, discriminating home and non-home charges, in breach of the spirit of its own Monetary Policy Statement of May 3, 2013. Though there is nothing wrong with the concept of cash handling charges, such a notion exists for bulk cash handling and not for small amount cash. Furthermore, a differentiation between home / non-home is implicitly intersol differentiation. In other words, imposition of cash handling charges makes sense so long as the charges are reasonable and that such a charge is made reasonably uniform across home and non-home branches. The action points to address these and related issues are as under.2014-10-26T00:00:00Z