Psychometrics has evolved as a subfield of psychology to become the science of measurement of unobservable individual characteristics.

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5
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0answers
24 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 ...
0
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0answers
10 views

How to test measurement invariance with PLS?

I have two questions about structural equations modeling: To perform comparisons of model estimates for different groups (3 clusters), do I always have to analize measurement invariance first? If ...
2
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3answers
172 views

Can statistics really be used in education to determine test scores?

I am a middle school teacher. My district prides itself on having the kids take 3 tests during the year to predict their score, and my teaching, on "the real test" at the end of the year. My question: ...
10
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2answers
187 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
145 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 ...
0
votes
1answer
52 views

Several items for one construct

I am a dummy in statistics but need to accomplish some simple survey analyses. My question is: if I have several questions (items) for one construct (say, questions JS1-JS3 for job satisfaction) with ...
2
votes
1answer
51 views

Validation of a questionnaire in a new population

I have 400 responses to a 20 item questionnaire which purports to measure an attitudinal constuct in medical students. The instrument was validated in the US for a single year of medical students and ...
0
votes
1answer
69 views

Calculating total score for a scale including polytomous and dichotomous items [duplicate]

I have a variable that is measured using a 13-item, 4-point Likert scale with the exception of one item (yes $=1$, no $=2)$. How can I calculate the total score for this variable?
0
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2answers
50 views

Can I turn a latent variable be treated as an observed variable?

I am a doctoral candidate and for my dissertation research I am using two standardized scales as independent variables. Because these have not been used with my particular population, I needed to do ...
1
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1answer
57 views

Using Ltm package to calclate 3PL some lines of data seem to go missing

I am hoping someone can help with the following: I have been trying to use the ltm package in R to get person fit estimates using a 3PL model. The problem I have been having is that I start off ...
1
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0answers
33 views

How to calculate differential item functioning when factor structure differs between groups?

I want to test for differential item functioning on a self-report measure between two groups (i.e., one with a disease one without). Differential item functioning refers to a measurement bias wherein ...
1
vote
0answers
143 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
200 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
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0answers
31 views

Map a normal distribution N(x,s) to an ordinal response variable

I am working on a simulation. I am going to extract a series of normally distributed values from a distribution N(x,s) whose mean x and variance s is known. I want to pretend that such distribution ...
4
votes
3answers
141 views

How to check psychometric type of scales?

It is well known, that there are diffrent types of scales (see Wikipedia Level of measurement). In psycholinguistics there is Semantic Differential technique. It uses a scale (usually 5 or 7 grades) ...
1
vote
1answer
241 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
758 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
180 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
0answers
89 views

Confirmatory factor analysis for a newly constructed questionnaire

I am about to develop a new questionnaire with 142 questions I have performed exploratory factor analysis and 30 latent factors were extracted. I was wondering if it is necessary to perform ...
1
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0answers
177 views

Doing CFA on a known theoretical model, but having problems with convergent and discriminant validity

I did a survey based on the UTAUT model / theory with standard questions used. The N was 150. I am trying to validate the model for my survey with structural equation modeling (via the AMOS software). ...
3
votes
1answer
137 views

Item response theory vs. summative Likert scale

If the items to be "summed" or combined to create an overall index are collectively the underlying construct (i.e. I am trying to measure compliance to an intervention which has different ...
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 ...
3
votes
0answers
89 views

Should I run measurement invariance if confirmatory factor analysis is not affirmative?

I have a repeated measures design for a Likert scale with 10 items. This scale is assumed to be unidimensional and this is one of the research questions along with the scales measurement invariance ...
0
votes
2answers
92 views

Should I use raw scores or profile scores for variables in a regression model?

I'm trying to build a regression model to predict subjective memory reports based on the following predictors: objective memory test, illness perceptions, verbal fluency, and mood. I also want to ...
1
vote
1answer
134 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
108 views

Summing up ordered items to a sum-score: implications?

It is common practice in psychology to add together ordered items to sum-scores, and then use these sum-scores for subsequent statistics. This is usually done without explicitly mentioning measurement ...
3
votes
1answer
271 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?
3
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0answers
329 views

Can I combine several ordinal questions to create an index and/or composite measure?

I am using a survey that contains several questions about various dimensions of performance for policy research institutes. Here, performance in the policy arena is unpacked into things like: ...
2
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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
1answer
222 views

IQ adaptive test items in 1pl, 2pl or 3pl IRT model?

Some adapative test systems (e.g. school assessment tools) use the 1pl IRT model, while others use the 2pl or the 3pl. When developing an adaptive IQ test, is there a rule of thumb about which model ...
1
vote
1answer
5k views

How to calculate validity of questionnaire in SPSS?

I have 3 types of questionnaires, A 15 item scale with each item on a 7-point Likert type scale. Six subscales each containing different number of items 21 subscales each containing 4 items. ...
1
vote
1answer
123 views

How to select next item in polytomous CAT / MIRT?

To make a Computerized Adaptive Test out of a sample of 20 dichotomous items a typical course of action would be to: 1) calibrate respondent data with a R package like mirt or ltm using Rasch, 2PL ...
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
148 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
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0answers
73 views

how to analyze necessary/sufficient relationship?

Good day! I'm a second year psych grad student. From my fascination with formal logic, I wondered (just personal; not homework) about how to statistically establish necessary/sufficient ...
1
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0answers
69 views

What coefficient could I use to calculate the relative difficulty of a test in relation to others using only mean and population standard deviation?

I have a series of tests, all of them of different difficulty, and from each of them I get an average score and a population standard deviation; e.g: ...
4
votes
1answer
123 views

IRT/Rasch modeling with very large N

I want to fit a 1-parameter IRT model on a questionaire with 15 questions and about six million people. Considering the large N, standard errors aren't essential. It looks like the IRT world is sort ...
0
votes
1answer
68 views

EFA on R: Classifying Observations

I am newbie for R and Stats. I am using EFA in R [psych library] to identify the latent factors underlying my data. I got a reasonable amount of factors matching my purpose. My question is once I ...
1
vote
2answers
309 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 ...
6
votes
1answer
200 views

EFA clearly supports one-factor, measure is internally consistent, but CFA has poor fit?

I am exploring the psychometric properties of a 10-item self-report measure. I have about 400 cases in two independent samples. The items are completed on 4-point Likert scales. An EFA clearly ...
2
votes
1answer
173 views

Comparing two logit or probit curves using a single parameter

I've conducted a psychological experiment on the same subject, under two different condition. For each condition I've collected the number of correct and wrong answer for each stimulus (number of ...
2
votes
2answers
257 views

How do I analyze a z-score to determine a difference?

My data are in SPSS. I teach in a nursing program. During their junior year, 68 students participated in a simulation scenario for heart failure. They were by rated by observers (0/1, did not do/did ...
5
votes
1answer
608 views

IRT in R: Does anyone know of an IRT item calibration function that can cope with NA's?

I have a dataset that looks like this. ...
4
votes
1answer
2k views

4 point and 5 point Likert scales in a new questionnaire

I'm looking to confirm whether having a 4 point Likert Scale for some constructs, and a 5 point Likert scale for other constructs will be suitable when developing a questionnaire? I have 7 constructs ...
0
votes
2answers
606 views

Error message from grm() in ltm: subscript out of bounds

I am analyzing a survey data set. One of the items in the survey is: ...
1
vote
0answers
300 views

Which correlation analysis is appropriate for binary and ordinal variables?

Violin players were asked to rate 5 violins from least to most rich on a [0 1], 0.05-increment scale, ...
3
votes
1answer
95 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
1answer
2k views

Understanding signficant interaction with non-significant main effects [duplicate]

Possible Duplicate: How to compute significant interaction estimates when main effect is not significant? I am an applied linguist and I am modelling responses to a vocabulary test taken by ...
2
votes
2answers
2k views

Likert scale and yes/no calculation of one score

My survey is based on observations and interviews. The observation questions are yes/no type questions and interview questions are 4 points. $1=$ never, $2=$ sometimes, $3=$ usually, and $4=$ ...