Latest Exam mailbag

Added later:

This one on z-stats:

Dear Professor,

In one question from the quiz,
Q) The z value for a point is the number of standard deviations a point is away from the mean.
Indicate True or False.
True ( ) False ( )

The answer mentioned is False.
However, as far as I know, Z=(x-mu)/sigma Which means that x=mu+sigma*Z.

So shouldn't the correct answer be True?

My response:

I agree. I also believe it is TRUE.

I remember a discussion about this with the AAs. The question bank, IMO had got the answer wrong. In any case, to avoid confusion, we ended up giving everybody the benefit of doubt on this one.

Sudhir

This one on MDS

When two or more brands are close to each other on a dissimilarity map, does that mean they are more dissimilar or they are more similar? Is a similarity map the opposite of a similarity map?

My reply:

No, spatial maps *always* depict similarities only. SO 2 brands close to each other on a perceptual map are more similar to each other than to any far off brand.

Dissimilarity scores can be transformed into similarity scores and then used as a distance measure in the MDS program.

Sudhir

Got these mails:

Dear Sudhir,



It is very confusing, in terms of which Lectures to study. It would have been great, if apart from the book chapters the Lectures were specified.



Most of us study for exam based on the lecture notes, and now I am not sure which lectures to really focus on.



Ex: One response on blog says MCQ questions based on Lec 3, 6 and 7 alone. So shall I skip Lectures 1, 2, 4 and 5 and be safe for the exam?



Regards,

R

My reply:

The MCQs are based on chapters only. Within the chapters, if anything has not been covered/mentioned in the slides, ignore it.

BTW lec 5 is the modeling primer. The non-MCQ part borrows from there quite a bit, as you can see from the practice exam.

I would say, read all the slides. And only the book chapters mentioned for MCQs. And within those chapters, only that portion which was covered/mentioned in the class.

Hope that helps.

Another common question:

Dear Professor,



The exam instruction mentions that 2 A4 papers, 2-sided cheat sheets allowed.

Just to clarify, does this mean 4 different sides of the cheat sheets?

My reply:

Yes Priyom.

The instructions mention this, IMO. 4 different faces of A4 page are allowed.

Another one:

Prof Voleti,

Sorry for bothering you with this mail-I haven't been able to cull out the relevant information from your blog. The chapters for MCQs have been specified in the TA's earlier mail so there's no ambiguity on that. However, the chapters for the rest of the exam are still not clear. Could you tell me specifically which chapters are coming and which portions to leave out.

Tks and Rgds

My response:

For the non-MCQ part, feel free to ignore the chapters and go by the lecture slides alone.

Use the textbook only for reference to clarify anything in the slides.

The practice exam is very much like what the real exam will be like. YOu can see that its based more on the modeling primer and regression than on anything from the textbook directly.