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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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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24 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
12 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
59 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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15 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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14 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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21 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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1answer
13 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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5 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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4 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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11 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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18 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
20 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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7 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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10 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
25 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
42 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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11 views

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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98 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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15 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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54 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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15 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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1answer
84 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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25 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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1answer
43 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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1answer
79 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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20 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
272 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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23 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
45 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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17 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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10 views

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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46 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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1answer
776 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 ...
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30 views

Minimum number of tested patients to have a reasonable ROC curve [closed]

What are the minimum number of tested patients and the acceptable prevalence percent required to have a reasonable ROC curve? for example, can I test a total of 16 patients, 5 are diseased and 11 are ...
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1answer
73 views

Is 0.40 Alpha score (KR-20) acceptable for a true-false test?

I have 10 true-false-Idont know test items. I codded correct responses as 1, incorrect ones and dont knows as 0. I got 0.40 alpha score (or KR-20). Do you think that this score is acceptable for such ...
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33 views

High reliability imply difference?

Suppose a test has scores between $0$ and $50$. Alice scores a $34$ and Bob scores a $42$. Does a high Cronbach's $\alpha$ imply that the Alice and Bob's scores are statistically significantly ...
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14 views

Intraclass correlation with a sparse rater-subject matrix

I'm working on a problem pertaining to the reliability of faculty evaluations of students. My dataset contains ratings of ~160 students given by ~50 faculty members. Most students are rated by 2 ...
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3answers
130 views

Probability that node A is connected to another node

Example: I have nodes A, B and C. A is connected to B and C. B is also connected to C. The link between two nodes have a probability to fail. For the link between A and B, the probability is pAB ...
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1answer
70 views

Expected lifetime of a device with two parts each having spares?

Consider a device with two parts : (1) and (2). Part (1) has 2 spares and part (2) has one spare. Lifetime of part (1) and its spares have iid exponential distribution with rate lambda. Lifetime of ...
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1answer
42 views

wondering about Negative alpha cronbach

I used a questionnaire that usually has a high Cronbach's alpha and that has a scale of 7 answers. I did a before and after (an intervention) evaluation and got a very very low alpha for the before ...
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4answers
195 views

Sample selection algorithms to ensure that training & validation sets are representative

Currently, I am encountering a question, which is how to selection representative samples (training set and test set, even validation set) from the whole data set? I would like build a classification ...
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25 views

How remove variables to a certain number from Cronbach's Alpha?

I'm looking to use Cronbach's Alpha for one of my independent variable from my questionnaire (it consist of 8 variables, meaning that 8 questions are testing for this one particular independent ...
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18 views

Choosing between two scales

I am investigating a scale of consumer ethnocentrism - CETSCALE. I do not have much knowledge in econometrics, scales, etc., however: a) research papers report that the standard 17-item scale is ...
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2answers
101 views

Reliability test, Cronbach's alpha or else

I have a set of questions for my research on Importance Menu Design towards Customer Purchasing Decision. After running Cronbach's Alpha for reliability test, it turned out less than 0.5 These are ...
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32 views

Kappa (interrater agreement) alternative for count-based data which results in inflated agreement at lower counts?

I have a data set where four coders are rating 800 items on various attributes. This is achieved by reporting a count of the prevalence of each attribute, e.g. rater 1 thinks attribute A appears in ...
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19 views

Estimating and using reliability metric with the same data

I'd like to know if it is reasonable to use the same set of data to estimate and use a reliability metric from repeated measures? I am mostly interesting by the minimal detectable change (MDC). But I ...
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60 views

Given MTTF and Number of Items, how to calculate failing parts with Time?

I am wondering how to make use of MTTF Here is the situation, I am given an MTTF for an item type x and a certain demand for that item in the next 25 years, say 100 parts that will be in operation ...
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168 views

Should I use both paired t-test and intraclass correlation coefficient to examine the interrater reliability of an instrument?

As title, I am assessing the interrater reliability of a questionnaire (actually a Barthel Index (BI)) performed by four assessors (A,B,C,D) on about 25 test subjects. I plan to examine the IRR from ...
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115 views

Using Cronbach's alpha to test reliability of a questionnaire

I administer a questionnaire to managers asking them to what extent they agree / disagree that they perform certain functions (listed in the questionnaire) on a scale of 1-5. The sample functions are ...