5
votes
1answer
30 views

Item reliability or fit in IRT-based adaptive tests?

My background is in machine learning and statistics, but I am relatively new to psychometrics and testing. Nearly all of the literature I've found on item reliability refers to Chronbach's alpha or ...
10
votes
2answers
192 views

Identification of useless questions from a questionnaire

I'm developing a questionnaire. To improve its reliability and validity I want to use statistical methods. I want to eliminate questions whose answers are always the same. This means that nearly all ...
4
votes
4answers
151 views

If a measure is valid (but not necesarily reliable), can it be consistently replicated?

I had this question on an exam, and I was positive that the answer was A. The Beck Depression Inventory is a scale intended to measure depression levels, with higher scores indicative of higher ...
1
vote
0answers
151 views

Intra- and inter- observer error, and the intra-class correlation coefficient (ICC)

I have 3 observers, who each perform multiple observations in which they count a phenomenon. I'm trying to quantify both inter- and intra- observer error for this study. I'm new to this and am finding ...
4
votes
1answer
222 views

Good internal factor structure but poor cronbach alpha?

I am running a CFA and getting good fit indices (CFI = .99, RMSEA = .01) for a uni-dimensional scale. However, when I test for internal consistency, I get poor Cronbach alphas (alpha = .6). I have ...
1
vote
1answer
249 views

Cronbach's alpha vs. KR20/KR21 in reliability studies

Should we calculate Cronbach's alpha instead of KR20/KR21 for measuring the reliability of an achievement test, or a test with dichotomous data?
9
votes
2answers
826 views

Where do the descriptors for Cronbach's alpha values come from (e.g., poor, excellent)?

It seems fairly common to describe Cronbach's alpha values as follows: α ≥ 0.9 Excellent 0.7 ≤ α < 0.9 Good 0.6 ≤ α < 0.7 Acceptable 0.5 ≤ α < 0.6 Poor α < 0.5 Unacceptable Where ...
3
votes
1answer
194 views

What is the correct use of Cronbach's alpha?

I am trying to use Cronbach's alpha in order to see if some variables are measuring the "same", but I have some doubts about the correct use: Can I compute alpha for numerical, ordinal or ...
1
vote
1answer
102 views

Two treatments - How do I compute reliability estimates like Cronbach $\alpha$?

I randomized my survey, and now I have my data on SPSS (and all cleaned up) but when trying to run my Cronbach's alpha I have a problem. Because I have two treatments (sexualised and normal) all my ...
1
vote
1answer
139 views

Using existing questionnaire

I will be doing my colloquium and will be using existing questionnaires. I would like to know if there are authors/authorities who say that an existing questionnaire need not be validated. The ...
3
votes
1answer
289 views

Cronbach's alpha negative result

What should I do if I am getting negative results for Cronbach's alpha? Is there anyway to adjust it?
2
votes
0answers
60 views

Is it appropriate to assess internal consistency on related items measured with different response formats within the same instrument?

In my survey, I grouped 67 unique counseling techniques that I thought were related to one another (based on theory and conceptual similarity) into six "counseling domains" using fairly intuitive, ...
2
votes
3answers
161 views

How can there be a standard deviation of true scores?

Dudek (1979) describes the following formula as "the standard deviation of true scores when the observed score is held constant" (p. 337): $SE_{est} = SD \sqrt{(reliability × (1 - reliability))}$ ...
4
votes
2answers
201 views

What is the reasoning behind the formulae for the different standard errors of measurement?

McManus (2012) discusses the three standard errors of measurement and provides the following definitions. $SE_{meas} = SD \sqrt{(1 - reliability)}$ The standard error of measurement is an estimate ...
3
votes
1answer
149 views

Why don't we square the reliability correlation when calculating reliable variance?

This question relates to situations where we apply some test to the same people at Time 1 and Time 2, and then calculate the correlation between scores at Time 1 and Time 2. I am reading the book ...
1
vote
2answers
317 views

What factors do I have to consider when deciding if creating a composite score using four t-scores is defensible psychometrically?

Edit: I've conducted an item analysis on four variables - two quizzes and two psychological attributes, namely emotional intelligence and happiness. Its a within-subject design with students as ...
3
votes
1answer
103 views

Omega H asymptotic

In the omega function in the psych package for R, we have several outputs including Hierarchical omega, Asymptotic omega and Total omega. I was reading about the outputs, but I find nothing about ...
1
vote
0answers
399 views

How to validate a survey when using Likert scale?

I have developed a very simple survey to measure the attitudes of students toward science fairs. It makes use of the Likert Scale and Open Ended Questions. Do you have a recommendation for the type ...
4
votes
1answer
362 views

Internal consistency reliability in item response theory models

How can internal consistency reliability of a test and of individual test items be quantified in Item Response Theory models? I know I can resort to Classical Test Theory, Cronbach's alpha, and other ...
2
votes
2answers
1k views

Omega vs. alpha reliability

I wonder if someone can explain what is the main difference between omega and alpha reliabilities? I understand an omega reliability is based on hierarchical factor model as shown in the following ...
2
votes
0answers
104 views

Testing graded response model thresholds for significance?

I have a data set in which two raters have each rated N samples using a 5-point ordinal rating scale. My primary interest is in whether these two raters make significantly different use of those ...
7
votes
1answer
272 views

What am I measuring when I apply a graded response model to the “Hunting of the Snark” dataset?

In another question, I asked about the statistical validity of StackExchange's "Hunting of the Snark" dataset, and whether or not we could draw any conclusions from its results. I measured a few ...
8
votes
2answers
2k views

How to reduce number of items using factor analysis, internal consistency, and item response theory in conjunction?

I am in the process of empirically developing a questionnaire and I will be using arbitrary numbers in this example to illustrate. For context, I am developing a psychological questionnaire aimed at ...
7
votes
1answer
837 views

How to perform inter-rater reliability with multiple raters, different raters per participant, and possible changes over time?

Participants were rated twice, with the 2 ratings separated by 3 years. For most participants the ratings were done by different raters, but for some (< 10%) the same rater performed both ratings. ...
5
votes
3answers
4k views

Is it acceptable to use Cronbach's alpha to assess reliability of questionnaire composed of categorical and conditional items?

Background: I have data on a questionnaire made up of categorical factual items. Some of them are binary and others have more than two categories. For example: ...
2
votes
0answers
270 views

Maximizing Cronbach alpha to select the number of variables that define a given construct

I can't seem to find this anywhere on the internet or in my books. I'm putting together a construct for an underlying variable. Is it acceptable to have a construct with two variables if that ...
11
votes
2answers
2k views

Assessing reliability of a questionnaire: dimensionality, problematic items, and whether to use alpha, lambda6 or some other index?

I am analyzing scores given by participants attending an experiment. I want to estimate the reliability of my questionnaire which is composed of 6 items aimed at estimating the attitude of the ...
5
votes
1answer
5k views

Intraclass correlation coefficient vs. F-test (one-way ANOVA)?

I'm a little confused regarding the intraclass correlation coefficient and one-way ANOVA. As I understand it, both tell you how similar observations within a group are, relative to observations in ...
6
votes
3answers
913 views

Validating an existing questionnaire into another language

I am doing research and trying to use a questionnaire that is available in English in another language. Is there a systematic approach for validating a questionnaire in another language? What ...
2
votes
1answer
2k views

Internal reliability for an ordinal scale

My teacher is asking whether it is possible to look at the Cronbachs's alpha when looking at the internal reliability of an ordinal scale. She thinks, because you use the mean of it, it is not ...
8
votes
4answers
1k views

Can one validly reduce the numbers of items in a published Likert-scale?

[edits made in response to feedback- thanks :-) ] Doh! More edits! Sorry! Hello- I am doing some rather rough and ready data collection with a survey sent out to healthcare staff using a published ...
3
votes
2answers
327 views

The best measure of reliability for interval data between 0 and 1 [closed]

I have 6 sets of interval data each of which between 0 and 1. Each set, calculated by a computer program, is related to the degree of similarity between some sounds (pairwise). What do you think in ...
14
votes
2answers
9k views

Inter-rater reliability for ordinal or interval data

Which inter-rater reliability methods are most appropriate for ordinal or interval data? I believe that "Joint probability of agreement" or "Kappa" are designed for nominal data. Whilst "Pearson" and ...
7
votes
2answers
668 views

Reliability in Elicitation Exercise

I am trying to calculate the reliability in an elicitation exercise by analysing some test-retest questions given to the experts. The experts elicited a series of probability distributions which were ...