• Veritas Prep
    Free Veritas GMAT Class
    Experience Lesson 1 Live Free

    Available with Beat the GMAT members only code

    MORE DETAILS
    Veritas Prep
  • e-gmat Exclusive Offer
    Get 300+ Practice Questions
    25 Video lessons and 6 Webinars for FREE

    Available with Beat the GMAT members only code

    MORE DETAILS
    e-gmat Exclusive Offer
  • Target Test Prep
    5-Day Free Trial
    5-day free, full-access trial TTP Quant

    Available with Beat the GMAT members only code

    MORE DETAILS
    Target Test Prep
  • Varsity Tutors
    Award-winning private GMAT tutoring
    Register now and save up to $200

    Available with Beat the GMAT members only code

    MORE DETAILS
    Varsity Tutors
  • Economist Test Prep
    Free Trial & Practice Exam
    BEAT THE GMAT EXCLUSIVE

    Available with Beat the GMAT members only code

    MORE DETAILS
    Economist Test Prep
  • PrepScholar GMAT
    5 Day FREE Trial
    Study Smarter, Not Harder

    Available with Beat the GMAT members only code

    MORE DETAILS
    PrepScholar GMAT
  • Magoosh
    Magoosh
    Study with Magoosh GMAT prep

    Available with Beat the GMAT members only code

    MORE DETAILS
    Magoosh
  • Kaplan Test Prep
    Free Practice Test & Review
    How would you score if you took the GMAT

    Available with Beat the GMAT members only code

    MORE DETAILS
    Kaplan Test Prep
  • EMPOWERgmat Slider
    1 Hour Free
    BEAT THE GMAT EXCLUSIVE

    Available with Beat the GMAT members only code

    MORE DETAILS
    EMPOWERgmat Slider

How the GMAT finds your score IV

This topic has 0 member replies
Kevin Community Manager Default Avatar
Joined
05 Jun 2006
Posted:
47 messages
Upvotes:
7

How the GMAT finds your score IV

Post Wed Jul 26, 2006 11:41 am
Last week, we continued our discussion of the "item characteristic curve," which ETS uses to determine whether a particular question is appropriate for you at a given point during your exam. This week, we will discuss the "inverse item characteristic curve" as well as the "estimator curve," both of which serve to help the CAT find your score.

If you recall, the item characteristic curve displays the probabilities of answering a particular item correctly for different ability levels.

The "inverse item characteristic curve", on the other hand, displays the probabilities of answering a particular item incorrectly for different ability levels. If, for example, the curve for an item indicates that someone performing at the 600-level has a 45% chance of answering the item correctly, the inverse curve for that item would indicate a 55% chance of answering the item incorrectly. This is because the probability of answering correctly and the probability of answering incorrectly must sum to 100%, since those are the only possibilities. In essence, then, each point on the inverse curve is simply 100 minus the probability of answering the item correctly for that ability level.



What is the purpose of the inverse curve? After every question, the CAT takes all the regular curves for the items you answered correctly and all the inverse curves for the items you answered incorrectly and multiplies all the curves to arrive at the "estimator curve" of your ability. Basically, the CAT determines the probability of your answer pattern by multiplying the regular and inverse curves.

_________________
Kevin Fitzgerald
Director of Marketing and Student Relations
Manhattan GMAT
800-576-4626

Contributor to Beat The GMAT!

  • +1 Upvote Post
  • Quote
  • Flag
Need free GMAT or MBA advice from an expert? Register for Beat The GMAT now and post your question in these forums!

Best Conversation Starters

1 lheiannie07 116 topics
2 LUANDATO 67 topics
3 swerve 66 topics
4 ardz24 61 topics
5 AAPL 59 topics
See More Top Beat The GMAT Members...

Most Active Experts

1 image description Scott@TargetTestPrep

Target Test Prep

213 posts
2 image description Brent@GMATPrepNow

GMAT Prep Now Teacher

177 posts
3 image description Jeff@TargetTestPrep

Target Test Prep

168 posts
4 image description Rich.C@EMPOWERgma...

EMPOWERgmat

133 posts
5 image description GMATGuruNY

The Princeton Review Teacher

126 posts
See More Top Beat The GMAT Experts