# Search results

1. ### 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...
2. ### 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...
3. ### 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...
4. ### 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...

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
6. ### 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...
7. ### 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...
8. ### 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...
9. ### 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)))...
10. ### 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...
11. ### 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...