Class Notes (866,995)
CA (523,442)
U of G (27,469)
PSYC (3,998)
PSYC 3250 (76)
Lecture

# PSYC*3250 Ch 5.pdf

5 Pages
124 Views

Department
Psychology
Course Code
PSYC 3250
Professor
Deborah Powell

This preview shows pages 1 and half of page 2. Sign up to view the full 5 pages of the document.

#### Loved by over 2.2 million students

Over 90% improved by at least one letter grade. are saying about us

OneClass has been such a huge help in my studies at UofT especially since I am a transfer student. OneClass is the study buddy I never had before and definitely gives me the extra push to get from a B to an A!

Leah — University of Toronto

Balancing social life With academics can be difficult, that is why I'm so glad that OneClass is out there where I can find the top notes for all of my classes. Now I can be the all-star student I want to be.

Saarim — University of Michigan

As a college student living on a college budget, I love how easy it is to earn gift cards just by submitting my notes.

Jenna — University of Wisconsin

OneClass has allowed me to catch up with my most difficult course! #lifesaver

Anne — University of California
Description
Friday, October 5, 2012 Chapter 5: Scales, Transformations, and Norms - raw scores, which represent simple counts of the behaviours sampled by the test or measuring procedure, do not always provide useful information - it is often necessary to re-express, or transform, raw scores into some more informative scale Scale - the set of scores that might be reported for a test - scales are very often transformations of the original raw scores Transformations - the simplest transformation is one that expresses scores in terms of percentage rather than raw units - this simple transformation has 3 characteristics than many of the most useful transformations exhibit: 1. It does not change the personʼs score; it simply expresses that score in different units 2. It takes into account information not contained in the raw score itself-here, the number of items on the test 3. It presents the personʼs score in units that are more information or interpretable than the raw score Linear Transformations - Transformed score = constant + (weight x raw score) - this form of a transformation guarantees a simple, direct relationship between raw scores and transformed scores that can be depicted using a straight line - the z transformation is extremely useful for a number of reasons - ﬁrst, the z score indicates each personʼs standing as compared with the group mean - when the distribution of raw scores is reasonably normal, z scores can be directly converted to percentiles - z scores are very useful in interpreting most psychological tests and measurements Variations of the Z Transformations - there are 2 features of z scores that are undesirable: half of the z scores in a distribution will be negative and z scores often have fractional values, even when they exceed 11 or 21 - several score transformations can overcome these disadvantages - the T score is a simple transformation of z that takes the following form: - T score - (z score x 10 ) + 50 Area Transformations - uses the normal curve to create scale score values - linear transformations simply change the units of measurement - e.g. changing Fahrenheit to Celsius - rather than simply changing the units of measurement, area transformations change the point of reference - these transformations express a personʼs score in terms of where it falls on a normal curve, rather than simply providing a new unit of measurement Friday, October 5, 2012 - percentile transformation/percentile rank - area transformations do not change the rank order of scores, but they do change the intervals between scores - you can easily convert z scores to percentile ranks - the transformation to percentile ranks is one of the most common and useful transformations of raw scores Stanine - a contraction of the term standard nine and represents one of the simplest transformations available - raw scores are transformed to a single digit between 1 and 9 Equating Scale Scores - in many instances, it is not possible or desirable to use the same test across different groups of examinees or for the same group of examinees at different times - if the same test is used twice, there are a variety of factors that complicate the interpretation of factors (student remembers the questions) - rather than using the same test twice, educators are likely to use alternative forms of the same achievement test - the question is whether the test published can be sure that both forms are equal in terms of their psychometric characteristics (difﬁculty) - there is growing interest in the problem of equating scores on different versions of the same test that use different testing technologies Equating Alternate Forms Administered to the Same Examinees - the simplest way to equate 2 alternative forms of a test is to distribute both forms of the test randomly to a large representative sample of examinees - random assignment is crucial to accuracy - the next step is to generate the descriptive statistics on both forms of the test - ﬁnally, a straightforward linear transformation (z scores) can take place, equating a speciﬁc raw score from one test to the scale score that it would equal on the second test Equating Alternative Forms Administered to Different Examinees - we actually have 3 tests: the old test, the new set, plus the common set of items given to both groups of people - the mechanism for equating the new test for to the old test form is through this common collection of item,s referred to as an anchor test - the information obtained from the anchor test provides data that allows one to equate the 2 test forms - if people perform differently on test forms A and B, it might be difﬁcult to determine whether this outcome reﬂects differences in people taking the test or differences in the tests themselves - the use of a common anchor test, which is taken by both groups of examinees, allows us to separate differences among examinees form differences between the test forms Norms - scores on psychological tests rarely provide absolute, ratio scale measures of psychological attributes Friday, October 5, 2012 - it rarely makes sense to ask how much intelligence, motivation, depth perception a person had - scores on psychological tests do provide useful relative measures - it makes sense to ask if Scott is more intelligent than Peter - one of the most useful ways of describing a personʼs performance on a test is to compare his or her test score with the test scores of some other person or group - a personʼs score is interpreted by comparing that score with the scores of several other people, this comparison is referred to as a norm-based interpretat
More Less
Subscribers Only

Only pages 1 and half of page 2 are available for preview. Some parts have been intentionally blurred.

Unlock Document
Subscribers Only
###### You're Reading a Preview

Unlock to view full version

Unlock Document
Subscribers Only
Notes
Practice
Earn
Me

Log In

OR

Don't have an account?

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view

OR

By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.

Request Course
Submit