Chip-kaalee!

It was around 8:30pm when a fast local to Badlapur arrived at platform number five of Thane station. A huge crowd of commuters were moving along the staircases at the time. Suddenly a loud cry, "Bachao,bachao!" baffled commuters and people started pushing one another on the staircases. Rahul Surve, a Thane resident, who was on the staircase at the CST end, said, "I was in the middle of thhe packed staircase when suddenly, all the women in the platform started shouting. Everyone, unware of the situation, started running up and out of the station....In a moment, the entire platform was empty of commuters. There wasn''t single person on it"

Jaikishen Gupta, an employee of a canteen located on the platform said, "we quickly pulled down our shutters,as we thought some kind of emergency had gripped the station". Some commuters on the platform jumped onto the tracks and a few unfortunate even fell into open drains between platforms.

Meanwhile, some commuters informed the government railway police about the commotion... the police could not fanthom what caused the panic and kept running from one platform to another, carrying a stretcher with them..assuming there was an accident".

When the police conducted an enquiry, the reason for the commotion completely baffled them. ..." It was a middle-aged woman who had shouted for help when a lizard (3 inches in length according to eye-witnesses!)fell on her from the roof of the train. people did not understand why she was screaming and instead of helping her, started running. Fortunately no one was hurt!.

Source: excerpts from a report- "How a lizard held Thane station to ransom",Mumbai Mirror edition-28th june 2008

Blog author's conclusion-railway officials should immediatly nab the accused "chip-kaalee" and charge fines for illegal travel on the roof of a train!..and the lady in this case should be recommeded for an award of the highest order for her "bravery in saving lives" of fellow commuters.

The secretary problem

The secretary problem is an optimal stopping problem that has been studied extensively in the fields of applied probability, statistics, and decision theory. It is also known as the marriage problem, the sultan's dowry problem, the fussy suitor problem, and the best choice problem. The problem can be stated as follows:

1. There is a single secretarial position to fill.
2. There are n applicants for the position, and the value of n is known.
3. The applicants can be ranked from best to worst with no ties.
4. The applicants are interviewed sequentially in a random order, with each order being equally likely.
5. After each interview, the applicant is accepted or rejected.
6. The decision to accept or reject an applicant can be based only on the relative ranks of the applicants interviewed so far.
7. Rejected applicants cannot be recalled.
8. The object is to select the best applicant. The payoff is 1 for the best applicant and zero otherwise.

Let us say that an applicant is a candidate only if it is better than all the applicants viewed previously. Clearly, since the objective in the problem is to select the single best applicant, only candidates will be considered for acceptance. One reason why the secretary problem has received so much attention is that the optimal policy for the problem (the stopping rule) has a surprising feature. Specifically, for large n the optimal policy is to skip the first n / e applicants (where e is the base of the natural logarithm) and then to accept the next candidate that is better than all those previously interviewed. As n gets larger, the probability of selecting the best applicant from the pool goes to 1 / e, which is around 37%. Whether one is searching through 100 or 100,000,000 applicants, the optimal policy will select the single best one about 37% of the time.

For an arbitrary cutoff r, the probability that the best applicant is selected is

Letting n tend to infinity, writing x as the limit of r / n, using t for j / n and dt for 1 / n, the sum can be approximated by the integral

Taking the derivative of P(r) with respect to x, setting it to 0, and solving for x, we find that the optimal x is equal to 1 / e. Thus, the optimal cutoff tends to n / e as n increases, and the best applicant is selected with probability 1 / e.

In summary:

Psychologists and experimental economists have studied the decision behavior of actual people in secretary problems . In large part, this work has shown that people tend to stop searching too soon. This may be explained, at least in part, by the cost of evaluating candidates. Extrapolating to real world settings, this might suggest that people do not search enough whenever they are faced with problems where the decision alternatives are encountered sequentially. For example, when trying to decide at which gas station to stop for gas, people might not search enough before stopping. If true, then they would tend to pay more for gas than they might had they searched longer. The same may be true when people search online for airline tickets, say. Experimental research on problems such as the secretary problem is sometimes referred to as behavioral operations research.

source: From Wikipedia, the free encyclopedia
related site:http://utilitymill.com/utility/Secretary_Problem_Optimizer

A temple cave

Batu Caves, Malaysia

Picture taken by: C.K.Venkataraman Reference:http://en.wikipedia.org/wiki/Batu_Caves

Time!...for game,set and match

The All England Lawn Tennis Club's-
WIMBLEDON Championships 2008
23 June- 8 July

ROLEX-The official time-keepers for a timeless event

to the estranged

"Nobody said it was easy,
Oh it's such a shame for us to part.
Nobody said it was easy,
No one ever said it would be so hard.

I'm goin' back to the start..."

-coldplay, the scientist

Rain Man

The iconic MRF Muscle Man declaring arrival of the monsoons.

Frames of Time

Published by: Hindustan Times
Pictures taken by: Kulwant Roy

Brunel University

Brunel University
Msc Distributed Information System(2003-2004)
Dept. of Information Systems and Computing