Website of Srikant Vadali
Adaptive Conjoint Analysis
I just now finished writing a web application to perform adaptive conjoint analysis (ACA) using perl. I will be using this application to collect data for a project that I am working on with Arvind Rangaswamy and John Liechty.
Click on the Research Lab link and use the user id ‘demo_aca’ to access a demo study. Leave the password box empty. I am in the processing of cleaning up the code and hope to release it under GPL in the near future. Any comments or suggestions about the interface will be very much appreciated.
Using Exec() via PHP on a Shared Host
For a recent project that involves generating questions on the fly in the context of conjoint analysis, I had to call a C++ executable using Exec() via PHP. I tried using the following code:
<?php
$output = array();
$return_val = -1;
$str = exec(‘./random_qn’,$output,$return_val);echo $str;
echo ” “;
echo count($output);
echo ” “;
echo $return_val;?>
The output when I call the above code from the browser should be:
0,1,2,3,4,5,6,7,8,9
1
0
Instead, the output I see is:
0
127
The interesting part of this problem was that the code was running fine from the command line but not from the browser. I found the answer after seeking the help of customer support of my web host (Futurequest).
It turns out that I was getting incorrect output because Exec() was unable to access a shared library used by my C++ code rand_qn. My bash profile had the correct LD_LIBRARY_PATH but it seems that exec(.) starts an empty shell and hence the shared libraries were not found at runtime. This above explains why the code was running from command line but not the browser.
The new code appears below:
<?php
$cmd = “LD_LIBRARY_PATH=path_to_shared_lib:$LD_LIBRARY_PATH && export LD_LIBRARY_PATH && ./rand_qn 2>&1″;
/* Note: exec(.) starts a new shell every time it is called. Thus, commands need to be combined like above.*/$output = array();
$return_val = -1;
$str = exec($cmd,$output,$return_val);echo $str;
echo ” “;
echo count($output);
echo ” “;
echo $return_val;?>
The above code worked. Thanks to Arthur of Futurequest for pointing me in the right direction.
Market Research for Entrepreneurs
Our college is presently planning to introduce a new graduate program targeted at entrepreneurs. We are planning to offer a course on marketing research in the proposed program whose tentative description appears below:
Market Research for Entrepreneurs
In this course students will learn and apply various marketing research techniques that will enable them to succeed as entrepreneurs. Some of the topics we will cover include: assessing customer needs, estimating market demand, deciding the features of the proposed product/service and the price that would be most attractive to their target market etc. The course will provide students with an overview of key marketing concepts, an understanding of the statistical methodology behind the market research techniques and practical application of the techniques via cases and projects.
I am excited about teaching this course but at the same time I wonder if there is anything that I should include/exclude in the course. Feel free to let me know if you have any feedback via the comments to this post. Thank you.
Selling Less for the Same Price
I just now read a news article which discusses the practice of various firms which are shrinking package sizes without reducing prices. For example, the article has the following example:
“They used to sell a 12 pack of Pepsi cans a year ago cost $2.00, then the price was raised to $2.50 and now they’re selling an 8 pack for $2.50,” said a shopper.
Is reducing the amount of product consumers buy without reducing price unethical? From an ethical perspective it seems like we are on thin ice here. It looks as if manufacturers are taking advantage of some consumers who may not realize that the new packaging has less of the product. But, to be fair manufacturers clearly print the amount of product in the package and hence it is equally legitimate to argue that they have informed consumers about the package change.
If reducing package size without changing price is unethical then keeping the package size the same but increasing prices should also be unethical. I am sure most consumers would agree that keeping the package size the same but increasing prices is an unattractive but ethical practice. By the same token, reducing the package size without changing the price is an ethical practice as long as manufacturers inform consumers about the new package size.
As for the consumers who do not realize the that the package size has shrunk: caveat emptor! Manufacturers should not be the ones to blame if consumers do not do their homework before purchase as long as the new package size is clearly mentioned on the package.
Equations in Microsoft Word 2007 Using Latex
In my research work (the academic type), I often have to write equations in Word. I do not use latex for writing my academic papers despite its power to typeset equations as the steep learning curve associated with it is prohibitive given my situational constraints (e.g., journals require a word document to be submitted). I would need to not only learn how to use latex to typeset equations but will also need to learn how to typeset text, tables, figures etc which seems too much work to me.
However, I have recently discovered that I can write equations in Word 2007 using latex commands. Learning to write equations using latex in Word does not involve a steep learning curve as it only involves a small subset of all latex commands. Using latex commands also saves enormous time as I no longer need to hunt around for the required symbol in Word 2007’s equation editor. In addition, word converts what I am typing to the appropriate symbol in real-time which enables me to make needed corrections as I type. However, before you take the plunge there are three issues you should know:
- Your co-authors must have Word 2007 to be able to edit the equations. They need not know latex as they can use the graphical interface to edit the equations.
- If you convert the document to Word 2003 then the equations will be converted into images which cannot be edited unless the document is re-saved as a Word 2007 document.
- Latex functionality is an undocumented feature as it does not appear in any of the official help files. Thus, it may disappear in any future updates to Word 2007 or in future releases of Word 2007.
Keeping the above in mind, here is a short tour of what can be accomplished in Word using latex. Before you use the commands below, you have to first insert an equation by using either the ribbon ([Insert][Equation]) or using the short cut [Alt][=] key combination.
- Small Case Greek Letters
- Upper Case Greek Letters
- Integral
- Subscripts and Superscripts
- Product and Sum
Type the following and hit spacebar:
\alpha \eta \nu \tau \beta \theta \xi \upsilon \gamma \iota \o \phi \delta \kappa \pi \chi \epsilon \lambda \rho \psi \zeta \mu \sigma \omega
The output will look like:
Type the following and hit spacebar:
\Gamma \Lambda \Sigma \Psi \Delta \Xi \Upsilon \Omega \Theta \Pi \Phi
The output will look like:
Type the following including keystrokes as shown:
\int[spacebar]_(-\infty)^(\infty)[spacebar]f(x) dx=1
The output will look like:
Note: The underscore character ‘_’ and the caret character ‘^’ can also be used to for subscripts and superscripts as shown next.
Type in the following and hit [spacebar]:
\x_1 \x^2 \x_1^2
The output will be:
Type the following as shown to create equations involving product and sum:
\prod[spacebar]_(i=1)^(n)[spacebar]x_i[spacebar]
\sum[spacebar]_(i=1)^(n)[spacebar]x_i[spacebar]
The output will be:
I hope the above gives you a taste of what is possible.
PS: There are minor variations in latex and the latex that word uses. For example, the latex code for the product equation is \prod_{i=1}^{n}x_i. Notice the difference in brackets (curly vs non-curly).
The Problem With Short Answer Questions
In my upper-level marketing courses, I typically ask undergraduates short answer questions that require them to apply a theoretical concept in an applied setting. An example of such a question is:
Initially, Huggies was in the disposable diaper industry. Then it developed Pull-Ups disposable training pants for kids who were in the transition stage between diapers and cloth underwear. What kind of a growth strategy did Huggies use when it developed this new product? Justify your response.
It has been my experience that students tend to give unduly verbose answers to short answer questions. This tendency is understandable as they want to provide comprehensive answers to avoid losing any points. However, there are two problems associated with long answers. One, grading the answers is a tedious task. As most instructors can attest, there is a wide variation in the writing skills of undergraduates. In addition, the pressure of an exam likely prevents even the better writers from providing a structured response. Thus, reading and trying to comprehend student responses is a difficult task. Second, the tendency to write long answers does not improve the student’s ability to communicate effectively: a short answer becomes long, a precise answer becomes imprecise and a well organized response becomes disorganized as they simply write without a plan.
I have tried three different solutions to address the above issue:
(a) Give them less space to write (perhaps half a page instead of a full page)
(b) Request that answers must be precise with the admonition that imprecise answers would be penalized and
(c) Impose sentence limits on answers (e.g., Limit your response to no more than 5 sentences) .
The first solution did not work very well for me as students would find creative ways to utilize all available space (e.g., write in the margins). The second solution works to some extent as the threat of penalties forces some students to be precise but it is not as effective as the third solution in curbing excessive verbosity. Imposing strict sentence limits seems to force students to organize their response such that they do not exceed the sentence limit. Interestingly, I have found an increased use of the eraser when I have imposed sentence limits as students re-write their first draft to accommodate my restrictions. It is the third solution that I use currently for all my short answer questions until a better solution comes along.
PS: The short answer to the question posed earlier is: Huggies used ‘product development’ to grow. Product development is a strategy which is used by an organization when it develops a new product targeted at their existing consumers. Pull-ups is a new product that is targeted at kids (perhaps a bit older than the ones who use diapers) and their parents.
The Begining
I have finally decided to start a blog. Starting this blog is primarily an experiment as I am not sure if I will be able to find either the time or the energy to post frequently. Time will tell.
The topics I will blog about will be about marketing research and marketing. I will share my experiences, thoughts and opinions on teaching, research and technical issues as they relate to the above topics. I do not know at what frequency I will post but hopefully it will be at least once a week.
Comments are always welcome.