How IBPS TWSS is calculated

Published on Friday, November 01, 2013
Many readers have requested me to explain how TWSS score is calculated by IBPS. Although IBPS have clearly mentioned in their website that TWSS scores are calculated by linear transformation method taking mean score = 25 and standard deviation = 5, here is the PDF file released by IBPS. Still many candidates unable to understand this formula as IBPS guide is bit incomplete and vague. Today I am explaining calculation of TWSS with an example. In case you still unable to understand the formula then please write a comment or mail me.

Check IBPS PO 2013 expected cutoff

1) Actual corrected score

Number of questions you attempted correctly minus negative marking (0.25 marks for question). For example Ram attempted 25 questions in reasoning section out of which 4 were wrong. His corrected score will be 21- 1 = 20. 

2) Equated score

Scores of candidates of every slot and paper set is equated according to difficulty level of the test. Difficulty level of the test is decided by marks scored by all the candidates in a particular question paper.
For example there 50 question paper set in IBPS PO 2013 (Just an example to explain the concept). In set 21 average marks of students is lower than average marks of students in other question sets. Automated computer program will equate the scores of all the candidates of set 21 by multiplying it with a equating value, for example 1.0122 or 0.986

3) Final standardized score

As announced by IBPS in their official website that they use Linear transformation method by taking mean = 25 and standard deviation = 5, to calculate TWSS of candidates.

Let's take an example to show the calculation :-

For example Raman scored 30 marks in Reasoning section of IBPS PO. What would be his TWSS score out of 50.

First of all we will calculate Z score

Z score = (equated score - actual average score of all candidates) / standard deviation
Now Z score will be dependent upon the average score of all the candidates and standard deviation of scores obtained. Here standard deviation is used to reduce the impact of very or very low scorers on the scores of remaining candidates.

Here we assume average score to be 15 and standard deviation to be 8.

⇒ Z score = 30 - 15 / 8 = 1.875

Calculate T score 

⇒ T score = Standard Deviation × Z score + Mean score

IBPS have mentioned in their press release that Mean would be taken as 25 and Standard deviation would be taken as 5.
T score = Standard deviation (given by IBPS) × Z score + Mean score (Given by IBPS)

⇒ T score = 5 × 1.875  + 25 = 34.375

⇒ Raman's Final TWSS in reasoning = 34 

Similarly we can calculate TWSS scores in remaining sections to reach final scores.

What to learn from TWSS calculation system

  • If you get a difficult exam slot then don't worry, your score will be equated by an automated system.
  • As candidates have no right to choose exam slot, you need not to worry about which kind of people appeared in your exam. This thing happens in CAT exam where candidates choose their exam slot and sharp candidates takes first slots and weak students takes last slot.
  • TWSS score is dependent upon average score of all the candidates.
  • There is no fixed cutoff for any section.

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