A measure is said to have a high reliability if it produces similar results under consistent conditions. DO NOT confuse reliability with validity (see tag wiki).

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Correcting for multiple data points

I am validating a new measure of therapist competency in psychology. I am getting 4 clients who have taken part in 40 sessions (10 each) to answer a questionnaires about their therapy sessions ...
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Inter-rater reliability: two raters rate dataset A and two raters rate dataset B how to combine it into one number?

Me and one other person (Alice) counted the amount of boys and girls playing on a school playground (consent of parents and school were given of it being videotaped). Two other persons (Bob and ...
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24 views

Test-retest correlation for panel data

I've run an experiment in which subjects rate how much they like six different objects on a 1-5 scale on two occasions. I'd like to obtain a summary measure of how consistent are the the subjects in ...
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1answer
67 views

Understanding of the chi square statistic

I have a formula for approximating the max the mean time between failures (MTBF) that is: r / operating time (*note-MTBF is 1/ failure rate) where r is the number of failures observed. I have ...
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18 views

Correct approach for computing interrater reliability

everybody. Can't find a strong answer to this "special case" elsewhere on the interwebs, so I'm hoping you can help. I want to computer interrater agreement (actually, in this case, inter-method ...
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1answer
20 views

acceptable ICC for 6-point Likert scale

I have pairs of pictures of participants making facial expressions (240 pairs per participant, 11 participants). Two raters agreed on a criterion and rated each one of the pairs on a scale from 1 to ...
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13 views

Assessing Repeatability: Random and Systematic Error

I am analyzing a study where my goal is to assess the quality (precision) of several machines. I have just one true value (measured with the goldstandard) and made 30 runs for every single machine. ...
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8 views

Fleiss Kappa: am I using it correctly?

I have a dataset where 20 subjects rated 16 audio samples according to some perceptual features on 1-9 scale and I am interested to measure agreement between raters. What I do is following: for each ...
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1answer
32 views

Lifetime estimate of components where only a fraction of them have failed so far?

I am attempting to calculate how long a component is expected to last and ultimately how many working components will be left at a future point in time. 800 have failed and 2200 are still working. I ...
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What are the most important components of an item analysis of a MCQ exam?

I'm analyzing results of undergraduate exams that range from 60 to 100 multiple choice questions. The number of students doing any given exam ranges from ~70 to ~1000. In all cases students select ...
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2answers
37 views

Quantifying consistency between two groups of raters

I have two groups of people, group A (62 people) and group B (8 people), and each person in each group responded to a test with the same 8 questions where the answer to each question was one of the ...
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18 views

Bootstrapping on Cronbachs Alpha? - Is it a good idea?

One can calculate a BCa-CI of Cronbachs Alpha, e.g. using the {psy}-Package. Is this generally a good idea? You can read here about a simulation study in this matter. ...
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15 views

Test retest reliability for a test taken multiple times

In our study, we would like to assess the reliability of a test measuring pitch discrimination thresholds. For this, we let participants take an adaptive threshold test (staircase procedure). We ...
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15 views

What method(s) exist(s) for the classification and reliability (Cohen's kappa) analysis of partial data?

I'm trying to set up a study in which I have many (about 700) images to classify. I need to measure expert judgements on this data set. Based on literature on the same subject, I am setting up a study ...
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25 views

Cronbach's Alpha

which types of items (Ordinal, nominal, scale) included in Cronbach alpha calculations? In other word, in my questionnaire i have a different types of questions (yes or no, Likert scale, and opened ...
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1answer
52 views

Finding the Maximum Likelihood Estimate in R [closed]

How do I estimate the parameters through MLE for a Likelihood function like. Note that the function has 2 multiply signs and there is a integration term in the second one.
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48 views

Interpreting summary of ICC results in R package “psych”

I have a dataframe "all.st.icc", where 27 subjects have measures of social behavior for each of 8 different years. First four rows of data are as follows: ...
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1answer
88 views

Why is backward elimination justified when doing multiple regression?

Does it not result in over-fitting? Would my results be more reliable if I added a jack-knife or bootstrap procedure as a part of the analysis?
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1answer
48 views

Reliability test in Likert scale

I have found a Likert scale measure in an article for global job satisfaction measure that included three items as follows; All in all I am satisfied with my job, In general, I don't like my job ...
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2answers
177 views

Cronbach's Alpha in Pilot Study: do I need to eliminate items if alpha is already > 0.7

In the Pilot Study, I am trying to confirm reliability of my scales: I'm performing Cronbach’s alpha test on 5 items that represent one construct of my research model (IV). I'm receiving α = .710 ...
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30 views

Test retest reliability

I tested subjects and repeated the test 2 times, so I did it 3 times in total. My question is: does anyone know how to evaluate the test-retest reliability? Is there another method (besides ...
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19 views

Which reliability index (if any) is appropriate?

Subjects were asked to endorse whether or not they have experienced various negative events (yes/no). I want to use a measure that is a sum of how many events they have experienced. Since this measure ...
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23 views

Rejecting subjects based on retest analysis

Are there objective criteria for rejecting subjects based on a test-retest analysis? Perceptual data on a discrete scale [1,...,9] for a number of users over groups of audio excerpts was collected. ...
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19 views

Split-half when intermediate values are equal

I am trying to perform a split-half for strategy use, however, as you can see the middle most users have the same score. What is the best approach to perform a split-half in this situation? Do you ...
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17 views

How to test the inter-rater reliability of a nominal coding process that generates ordinal data?

A researcher studying hunger on a tropical island asks respondents, "What did you eat for lunch yesterday?" and the possible choices are "(4) Nothing; (3) a banana; (2) an unripe coconut; (1) a ripe ...
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9 views

Conceptual difference between ordinally reliable and nominally reliable inter-rater statistic, K-alpha?

Using Krippendorff's alpha allows one to calculate an inter-rater reliability statistic on nominal, ordinal, interval, ratio, and other types of data. Assume that Krippendorff's alpha is 0.6 when ...
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24 views

Composite reliability in CFA: how to treat the negative factor loadings?

I just have a simple, stupid question. For the composite reliability calculation, we start with summing all standardized coefficients for each factor. What if the signs of some of them are negative? ...
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30 views

how to estimate scale variance only using item sd's and scale reliability

The problem I encounter is that I need to estimate the scale variance of a psychometric scale without having the original data. The only information I have is the means of the (binary) items, their ...
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1answer
26 views

Where I can find resources to learn how to calculate the sample size representativeness, and realiability and validity of questionnaires?

I'm totally newbie in psychometrics but starting from a research paper with full data I would like to understand: how to calculate if the sample size is representative; how to calculate reliability ...
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15 views

Inter-rater reliability for $k$ raters with $0$ to $n$ of $n$ categories applying to each subject

I have a data set for which I would like to calculate the inter-rater reliability. However, this data set does not seem to fit the typical models that conventional algorithms allow for. My data set ...
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14 views

Kendall's W for random subjects (not raters)

I have 5 raters (A,B,C,D,E) who evaluated 60 images on 1 to 10 points scale. The images are split into two groups: half of them were easy, half of them vere difficult (1 is easy, 10 is difficult). I ...
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1answer
27 views

An invalid questionnare with valid resultant scores?

In what situation, a questionnaire could be invalid but its resultant scores could be valid? I received a comment from a journal article reviewer that says: In keeping with the preferred ...
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2answers
56 views

Should I use paired t-tests or ANOVA when comparing multiple variables from 2 tests?

I had 50 subjects perform two 30-minute cycling time trials on separate days. I would like to compare the means of several variables from each of the two tests: Cadence, Heart Rate, Power Output, and ...
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Negative Reliability for Pre Assessment BUT Okay Reliability for Post Assessment

I have gathered data from only 6 participants participating in a program. Before running my analysis, I wanted to check my reliabilities. The 2 item PRE assessment has a negative alpha. However, when ...
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221 views

sample size for test-retest reliability

I am interested in estimating the following: test-retest reliability for ordinal items; test-retest reliability for interval-level scale scores consisting of the items; and the optimal sample size ...
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18 views

How many number of items should i include in my test?

I have designed two post test ,a recognition test and a production test.I have inserted 18 items in each test. As I sifted through articles , I 've read that we should include at least 30 items to get ...
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84 views

Examining Validity and Reliability of a new questionnaire (Likert scale)

I need to examine the psychometric properties of a newly developed questionnaire. There are 22 items with a 5-point Likert Scale. The designed questionnaire includes two main scales. How do I ...
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21 views

The Effect of Unreliable Observed Variables in Factor Analysis (FA)

My question relates to the impact of unreliable observed variables in common factor analysis. Does common factor analysis treat the unreliable portion of a variable's variance as a unique variance? ...
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152 views

What is the statistic to calculate Cronbach's alpha for Polytomous items in R

Does anyone know, what is the function which can calculate Cronbach's alpha for polytomous items with different categories in R? Thank you
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32 views

PCA reduction and low-reliability components

I'm working on a survey with 288 observation in total (108 complete answers used) and around 200 variables. I'm working on reducing those number using Principal Components Analysis, using R. Suppose ...
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47 views

How to know if my data is balanced or imbalanced for an ROC curve analysis?

I am doing a research on the reliability of different models in detecting hidden defects in a test specimen. I have made a test specimen with defect prevalence about 25% (12 positive out of 49 total ...
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109 views

Calculating Cronbach's alpha: Same scale, multiple instances

I'm working on data analysis for my dissertation, and I'm banging my head against the wall when it comes to Cronbach's alpha. I just completed a pretest; after data cleaning, I have 119 valid and ...
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22 views

Is it possible to incorporate on/off cycles into a product's failure rate prediction along with its field failure rate and test data?

If I have a electronic module whose failure rate I am calculating using the chiinv() function in Excel, and the following data available to me: -test failures and test hours for the module and the ...
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2answers
393 views

Reliability in IRT Style

Reporting 'reliability' in IRT is more to 'informations' obtained and a bit different from a classical way using such as Cronbach alpha and KR20. Therefore, how to report the test reliability in ...
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30 views

f-test in context in scale reliability

In SPSS I have Scale->Reliability test. I used it for finding Cronbach alpha for my scale (11 items overall). However, in the same window in SPSS there is a checkbox "ANOVA TABLE -> F-test". I do not ...
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2answers
50 views

Cluster analysis as a preliminary analysis

I want to produce four groups (high/high, high/low, low/high and low/low) using two continues variables and compare these groups in terms of a few dependent variables. I know that cluster analysis ...
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24 views

Converting split-half correlations into coefficient of determination

It's my understanding that after finding the correlation (r) for a split-half correlation, you should convert that into a more accurate number via the Spearman-Brown formula, 2r/(1+r). Now I want to ...
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Split thirds correlation

You hear about split-half correlations often as a measure of reliability. But is there a reason that split-third correlations (or split-fourth, split-fifth, etc.) are never used? Shouldn't they ...
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52 views

Fleiss' Kappa alternative for inter-rater reliability with multiple answers

I have a dataset where researchers assign a binary yes/no answers to cells in a matrix. For each row more than one, but at least one, 'x' is allowed. For example, researchers 1 may code: ...
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1k views

Cronbach's alpha in R

I am pretty new to Cronbach's Alpha, so I have a question about how to find it using R. As far as I am aware, Cronbach's alpha is a measure of internal consistency, but to use the alpha() function in ...