Psychometrics Made Easy

Certification Exam PreparationJanuary 15, 2015

F. Sam Griggs, Jr., CCP, Cost Engineering Consultant

IntroductionWhat Is It?

How Did We Get Here?

What Is Its Language?

What is the Process?

How Can You Pass the Exam?

Your Technical Paper

Measurement

Theory

Technique

Psychometrics

Psychometrics

Psychometric

s

Statistical Research Effect on

Measurement

Objective Measurement of Skills and Knowledge 

Key Concepts are Reliability

& Validity

How Did We Get Here?

8 Hour Hand Written Exam

ComputerizedTesting

Statistical Data

Psychometrics Review

Removed Difficult

Questions Most Got Wrong

Removed Easy

Questions Most Got

Right

Grading:

To determine a passing grade of any test, it must be justified with empirical data.

It should be legally defensible.

Meet the Standards for Educational and Psychological Testing.

Glossary of TermsAlpha Coefficient

Angoff Method

Distractor

Item Difficulty

Item Distraction

Cutscore

Key

Glossary of TermsMean

Mean P

Mean Rpbis

P-value

Point Biserial Correlation (Rbpis)

Standard Deviation

Standard Error of Measurement (SEM)

Glossary of TermsReliability

Validity

Test Bias

Negative Correlation

SME

William H. Angoff Distinguished research scientist

at ETS for more than 40 years.

Angoff Method: One of his many contributions to psychometrics.

Author of “Scales, Norms, and Equivalent Scores”.

Angoff Method:

Most widely used

• Determines the passing % or cutscore.

Relies on SME

• SME are subject matter experts who examine each question.

• Predict how many minimally qualified candidates would answer correctly.

• The average of the SME’s predictions becomes its predicted difficulty.

• The sum of the predicted difficulty values averaged is the recommended cut score

Goal• Rate each test item • To determine whether a minimally qualified

candidate would answer the item correctly or incorrectly.

Mechanics of Psychometrics

Statistics

Validity

Reliability

ReliabilityA Reliable Measure: Measures test items

consistently across time, individuals, and situations.

Reliability is necessary, but not sufficient for validity.

Alpha Coefficient

RetestTest

Validity

Valid Measure: Measures what it is intended to measure.

Sample question: What is the capital of Texas?

This question is a reliable measure but would not be a valid measure for the CCP exam.

A valid answer might be Houston.

A valid measure for a CCP exam must measure only CCP components such as Cost Estimating, Scheduling, Project Management, etc.

Negative Correlation

This Negative number indicates that those who did well on the overall exam actually performed very poorly on this particular item.. Sometimes it indicates that the answer might be keyed incorrectly.

Sample question: What is the capital of Texas?

In this case, some candidates who passed the overall exam did not get this question correct – as marked. They selected the distractor “Austin”.

A valid answer was thought to be “Houston” and was erroneously marked as correct answer.

This statistic shows that a dis-proportionate number of successful candidates missed this question. So, those questions with Negative Correlation are reviewed very closely. Sometimes, candidates “over-think” the question.

Test Bias

A form of systematic (non-random) error which leads to examinees from one demographic group having an advantage over examinees from another demographic group.

Test bias may cause differences in average scores across demographic groups.

Example: USA uses different system of measurement than Europe. They use metric system so they may have problems with our questions re measurement.

But differences in group scores are not sufficient evidence that Test Bias is present.

AACE Certification Board has committee working on problem – Goal is to reduce Test Bias.

StatisticsBoth Reliability & Validity can be assessed

Statistically.

P-Value (Pass Rate or Item Difficulty)Point Biserial Correlation (Rbpis)Negative Correlation

Alpha Correlation

Statistical Assessments:

Easy Test Question90% tested answer correctly.

Sample Question:

What is the Capital of Florida?

a. Miamib. Tallahasseec. Jacksonvilled. Orlando

Easy Test Question

Sample Question:

What is the Capital of Florida?

a. Miamib.Tallahasseec. Jacksonvilled. Orlando

Hard Test Question50% tested answer incorrectly.

Sample Question:

What is the Capital of Michigan?

a. Detroitb. Ann Arborc. Lansingd. Kalamazoo

Hard Test Question Alternative is to change

distractor(s)

Sample Question:

What is the Capital of Michigan?

a. Detroit – change to say, Bostonb. Ann Arbor – change to say,

Cloquetc.Lansingd. Kalamazoo

Hard Test Question50% tested answer incorrectly but what if we

changed distractor answers?

Sample Question:

What is the Capital of Michigan?

a. Bostonb. Cloquetc. Lansingd. Kalamazoo

Hard Test Question

Sample Question:

What is the Capital of Michigan?

a. Detroitb. Ann Arborc.Lansingd. Kalamazoo

Sample of Math QuestionLess than 60% tested answer incorrectly.

Sample Math Question:

What is $5,100 invested at 12% compounded yearly, at end of 6 years?

a. $5,712b. $8,988c. $10,066d. $98,950

Solution to Math Problem

Solution : There are a couple of different ways to work this.

Start Begin Rate End

Year 1 $5,100 1.12 $5,712

Year 2 $5,712 1.12 $6,397

Year 3 $6,397 1.12 $7,165

Year 4 $7,165 1.12 $8,025

Year 5 $8,025 1.12 $8,988

Year 6 $8,988 1.12 $10,066

Sample Math Problem - Tips for Solution

There are a couple of different ways to work this example.

Solution : Work up a Table shown on previous slide.

Solution : Remember the formulas. There should be some basic formulas you want to remember.

Solution : Remember the ‘Rule of 72”. To determine the amount of time to double an investment, divide 72 by the interest rate. In this case, 72/12 = 6 years. The $5k should double and maybe answer is approx $10k.

Get rid of obviously wrong answers. These would be answer a and d. Answer a is too small and d is too high. That narrows it down to 2 plausible answers. If you had to guess, odds are 50% instead of 25%.

Certification Board Review:

Review the question to confirm that the marked answer is correct.

Change the wording of the question.

Modify the distractor to add or decrease the difficulty.

Make no changes.

Retire the question.

Steps in Making the Question Easier or Harder

Top Tips to Get a Great Score

Purpose •Understand the purpose of the exam.

Expect •Know what to expect in the timed testing environment.

Attitude •A positive attitude is a most.

Top Tips to Get a Great Score

Practice•Especially necessary for anyone who has never taken a Psychometric Exam.•Find websites & books that have practice test.•Focus on tests that specialize in your area(s) of weakness.

Time Yourself •Test yourself working against the clock.

Broaden Sample Test•Don’t rely only on the study guides.•Use AACE Recommended Practices (RP) on their web page.•Many of the new questions on exams come from the new RPs.

Top Tips to Get a Great Score

Refresh Math Skills

• Fact 1: AACE has Math Questions that other exams do not.

• Fact 2: Cost Engineers are expected to know the Rate of Return and other Math problems.

Get a Good Night’s Sleep• Make sure you get a good night’s sleep before

the exam so you are fully alert.

Follow Instructions• Carefully read or listen to the instructions on

taking the exam.

Top Tips to Get a Great Score

Answering Questions

• Trust yourself…Usually your first answer is correct.• Answer easy questions first, skip those you get

stuck on.• At the end, return to the questions you skipped.• Do not leave any questions unanswered. Eliminate

all obviously wrong choices.• Last resort…Guess if you need to as you have a

25% chance of getting it right.

Complete the Feedback Section on Exam

• Complete the Feedback Section at the end of the exam.

• Your comments or concerns help the Reviewers modify and improve future exams.

Don’t Give Up

• Keep trying until you Pass!• Identify what areas that kept you from passing.• Study these problematic areas to improve your

skills.

Conclusion:

Achieve

Certification

Use Angoff Method

Learn the Language

Implement ProcessesStudy &

Prepare for Exam

Technical PaperImportant information you should know before writing your paper

Tips for a Winning Paper

Table of Contents

Introduction: Purpose & Background

Basis & Analysis of Your Data

References

1

2

3

4

5

Abstract

Make sure your paper Includes:

Tips for a Winning Paper

Graphs or Tables to Support Premise

Logical Conclusion

Do Word Count: Minimum 2,500 Req.

Extra Points for Appendix

6

7

8

9

10

Organization & Clarity

Make sure your paper Includes:

Questions??