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    Significance test to compare two effect sizes (Cohen's d)

    I have two Cohen's D effect sizes from the same sample. How can I test if the difference between the magnitude of these two effect sizes is statistically significant? As the confidence intervals of the two estimated effect sizes overlap, can I assume that the difference between them is not...
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    How to linearly transform variables before t-test if their range is unknown

    I want to conduct a paired t-test to estimate the difference between two variables x1 and x2. For sake of simplicity, let's assume that the two variables measure how well participants in a study performed on two cognitive reasoning tests. In the first test (x1, float), participants receive a...
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    Basic questions about pre-/post-treatment comparison and z-standardization

    Assume I have three treatment-groups, each with pre- and post-treatment measurements: set.seed(42) n <- 100 df <- tibble( group_a_pre = rnorm(n, mean=0, sd=1), group_b_pre = rnorm(n, mean=50, sd=10), group_c_pre = rnorm(n, mean=5, sd=2), group_a_post = rnorm(n, mean=0.36, sd=1.2), group_b_post...
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    Help me understand the unidimensionality assumption in test theory (CTT and IRT)

    De Ayala (2009) writes: This always made sense to me until recently. In any statement found in a psychological questionnaire, there is semantic overlap between constructs. Heck, we even allow factors to be correlated in obliquely rotaded PCAs and EFAs. As soon as any two factors are...
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    Factor loadings > 1 in CFA with lavaan

    Hi folks, What are potential causes for factor loadings > 1 in CFA with lavaan? I'm using standardized loadings (std.lv). Is this generally concerning? Thanks
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    Testing hypothesis of difference in factor loadings across multiple scales in two questionnaires

    I'm unsure of how to test this hypothesis and would greatly appreciate your ideas: For illustrative purposes, let's assume that two groups of people (experts vs. novices) author a questionnaire with five scales (scale1 to scale5). Let's further assume that I have reason to hypothesize that when...
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    Comparing two dependent, non-overlapping correlations

    I have two questions regarding the comparison of two correlation coefficients from a single (paired / dependent) sample: Is it legitimate to use a test for comparing independent correlation coefficients instead? My understanding is that the only drawback is that this would compromise power...
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    Suspicious about perfect fit in SEM (CFI = 1, RMSEA = 0)

    I'm new to path analysis in SEM and suspicious about my model fit indices in R / lavaan: lavaan 0.6-6 ended normally after 27 iterations Estimator ML Optimization method NLMINB Number of free parameters...
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    GLM with multiple categorical predictors

    Hello internet, lets say I want to predict an outcome using multiple categorical predictors. Please consider the follow reproducible R-code: library(dplyr) library(psych) set.seed(42) n <- 500 df <- data.frame( loneliness = round(runif(n, 0, 1)), pet = factor(round(runif(n, 0, 1)))...
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    Confusion over the F-ratio in a hierarchical multiple regression

    Hey all, I'm not used to work with multiple regression analysis, so I would be glad if anyone could help me interpreting this result: I performed a hierarchical multiple regression in SPSS (forced entry) in two Blocks to predict to variable SM: Block 1: Predictors: IQ, AGE Block 2...
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    Urgently need help with data analysis

    Hey folks, i really am desperate for help with this, since I have to present my results at a conference in less than two weeks. I am a statistics-noob undergraduate psychoglogy-student, so please go easy on me. Research and Variables I want to examine the correlative relationship between a...