Wednesday, November 23, 2011

Duckworth-Lewis Method (part 3)

  1. Duckworth-Lewis Method (part 1)
  2. Duckworth-Lewis Method (part 2)

After giving an introduction of Duckworth-Lewis method and some examples of Duckworth-Lewis method in the previous posts this post focuses on the  Duckworth-Lewis method and some of the previously used methods in rain affected games.

Before the invention of this method there have been several other methods used at the international level to decide the result of a rain affected match.One of them was the run rate based system. The main disadvantage of this method was that the number of wickets fallen was not considered. Thus in this system if a team has scored 100 runs for the lost of 9 wickets the position of the team is considered higher than scoring 90 runs for the loss of 1 wicket.

Eng v SA World Cup 1992
Situation at end of match SA need 22
Also another method that was used is the Highest Scoring Overs method which compares the maximum runs scored by team1 in any set of overs equal to the number of completed overs received by team 2 against the team 2 in those completed overs. So if team 2 received 31.4 overs their score after 31 overs is compared to the highest scoring 31 overs of team 1's innings. So this method becomes very unfair as the maidens bowled by the second team is not considered. So eventually this method is more biased towards the first team. The most controversial usage of this method arises in the 1992 world cup semi final between South Africa and England. Play was halted when South Africa had scored 231/6 from 42.5 overs against England's 252/6 from 45 overs. When play was able to resume there was time for South Africa to receive only one more ball, 43 overs in total, so their target was revised to 252 by discarding the two maiden overs in the England innings, one of which yielded one extra. So the number of bowls available was reduced by 12 but the target remained unchanged. Due to the use of this method an apparently attainable target suddenly became an impossible one. 

There are many other methods used in a rain affected match. All of these methods either uses the run rate , highest scoring overs or pre-calculated curves (as used in Duckworth-Lewis method) with slight variations. Yet Duckworth-Lewis method is regarded the best method so far usedBut a slightly different method named as VJD system introduced by V.Jayadevan (an engineer from Thrissur in Kerala) has challenged the Duckwoth-Lewis method recently. 

Friday, November 18, 2011


First they came for the communists,
and I didn't speak out because I wasn't a communist.

Then they came for the trade unionists,
and I didn't speak out because I wasn't a trade unionist.

Then they came for the Jews,
and I didn't speak out because I wasn't a Jew.

Then they came for me
and there was no one left to speak out for me.

 A famous statement attributed to pastor Martin Niemöller (1892–1984) 

Tuesday, November 15, 2011

How Secured is Your Security Question ????

You may have seen different kinds of questions such as "What is your library card no ?" , "what is your mothers birth town ?", while registering for an online account.These questions are used in password recovery processes and additional sign in verifications. Normally we all care about our passwords and worry about the security of the password.

But do we really care about these security questions ? It seems most of us don't care much about these.Most of the time we give our real details as the answers to theses questions and simply forget about the security question.Even I was unaware of security questions selected for my email address until i decided to write this post.The most surprising thing is that I can't come up with the correct answer for those questions.I think this is common between most of us.We really DON'T CARE about those.

But in reality this is a great security risk.Even if you have a very good password that can not be guessed easily,you may be vulnerable to security threats.It is like locking the front door while leaving the backdoor open.The confidentiality of the answers for a security question will be far less than a password.If some one asks you a password you probably wont tell.But if some one asks you the birth town of your mother you may answer it.Also most of the details that are asked in security questions can be found publicly or can easily be guessed.That is what happened with the email account of Sarah Palin the vice president candidate during 2008 elections.

A good security question should have a answer which can be easily memorized, which is not publicly available and which does not change overtime. Further the possible number of answers for the question should be very large so that it can not be guessed. There are some websites which offers good security questions. But it is worth to note that the goodness of the question depends on the expected answer as well.

Thursday, November 3, 2011

Pigeon-Hole Principle

It's amazing how a very simple and obvious thing in life become a mathematical principle and helps to prove many complex results. Pigeon-Hole principle is one such concept. At first it seems as a very obvious fact and one may wonder whether it deserves such a place in mathematics. But this principle becomes very useful in many occasions to prove that there exists some answer for a problem.