1. C

    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...
  2. shannahw

    Normally distributed errors assumption is violated (multiple regression)

    Hi guys, I am testing the normally distributed errors assumptions for multiple regression with a visual inspection using a P-Plot plot. Now, I have the suspicion that the errors are not normally distributed (see image below). I have two questions about this: Is there any way to test this...
  3. S

    Assumptions for a 2 x 2 repeated-measures ANOVA

    I am currently working on a 2 x 2 repeated-measures ANOVA (rmANOVA), and I am unsure as to which assumptions I need to investigate and how to investigate them. It's a behavioral experiment. I have 30 subjects and 4 (2 x 2) measurements from each of them. There are equal sample sizes (30) in each...
  4. N

    LOGISTIC REGRESSION ASSUMPTIONS - linearity for categorical IV's

    Hi! I am going through the assumption for a logistic regression but I am stuck on making sure the 'IV is linearly related to the log odds'. My DV is dichotomous and all of my IV's are categorical (some binary, others with multiple groups). I am struggling to test this assumption on my data as...
  5. M

    Linear regression analysis assumptions not met

    I want to demonstrate a possible association between a dichotomous independent variable and a continuous dependent variable. Therefore, I wanted to use a linear regression analysis. However, the dependent variable is not normally distributed, while normality is an assumption of linear regression...
  6. I

    Are these valid assumptions / procedure for hypothesis testing?

    I will explain the problem at hand below. Italics means I have doubts on the accuracy of the statement and want to find out if it is correct. There are two call centers (A and B) having similar number of agents. Similar number of calls are dialed per month from each call center offering...
  7. M

    Chi squared test assumptions not met

    I want to perform a univariate analysis to predict if a higher BMI is associated with an increased incidence of complications after surgery. I divided the BMI of patients in 4 categories (<18.5; 18.5-25; 25-30; >30) and complications in 2 categories (yes; no). I tried to use the chi squared test...
  8. DanaDana

    Mean of the residuals in Simple Linear Regression *Beginner Alert*

    Hey guys, First of all, I would like to apologize for the question I'm gonna ask regarding the fact, that I am absolute beginner in statistics. Currently I'm trying to test some hypotheses in Rstudio using Simple Linear Regression, as I am aware that before interpreting results of my model I...
  9. T

    Data help!

    I am struggling to work out how I should analyse my data. My current thinking is that a chi squared test of independence will work, however only if the data I have can be set out in the correct format. I am testing 2 IV's that are varied within each trial randomly, where each trial has a cue IV...
  10. O

    Normality: DV itself or residuals?

    I always thought that we should be testing the assumption of normality by looking at the distribution of the DV in our design (by each level of the IV). But I keep seeing people talking about the residuals of the DV. For example, in ANOVA (and I suppose by extension the t-test and regression)...
  11. B

    Assumptions multiple regression violated

    Hello, I’m writing my thesis about the question: is ruminative thinking an independent risk factor for predicting marihuana use (controlled for sex and depression). In this study there are 300 participants of which 60 used marihuana. To investigate this relationship I wanted to do a multiple...
  12. M

    Binomial logistic regression linearity assumption with categorical variables ?

    I am trying to run a binomial logistic regression, and would like to check the linearity assumption. However all the resources I'm reading discuss the procedure for continuous variables, and I am only working with ordinal/categorical predictors. Can someone take me through it step by step, or...
  13. K

    MANCOVA MANOVA_assumptions_ heterogeneity of regression slopes

    Hallo there :wave:, I am examining the difference in illness models (by asking several questions: DV) for refugees and non-refugees (IV) (both n= 100). In addition, we asked about several confounding variables / covariates (demographic data). I hypothesis that DV (illness model) will differ...
  14. K

    MANCOVA MANOVA_assumptions_ heterogeneity of regression slopes

    Hallo there :wave:, I am examining the difference in illness models (by asking several Likert scale type questions: DV) for refugees (n=100) and non-refugees (IV)(n=100). In addition, we asked about several confounding variables / covariates (demographic data). I hypothesis that the illness...
  15. S

    Assumptions of linearity for parametric tests?

    Do parametric tests make assumptions regarding linearity? Whether yes or no, how can I explain this? It seems to me as though regression analyses assume linearity, but I can't seem to figure out whether these can be parametric tests or not. Many thanks!
  16. S

    ANCOVA assmptions not met.

    Hi, What is the non parametric alternative for parametric ANCOVA if we find that some ANCOVA assumptions are not met? How it can be done in SAS?
  17. A

    2x2 Anova, im struggling to report the assumptions

    Hello, I've ran a 2x2 anova and am trying to report the assumptions but would like to make sure ive done it correct, statistics is my weak point! I have tested normality and homogeneity and also tested for skew and kurtosis. Then am I supposed to report the means and the significance levels...
  18. F

    Violating Linear Regression assumptions

    I have a dataset in which I am performing linear regression with multiple covariates. The goal of the analysis is to identify important covariates (categorical and continuous) which have an important effect on the response. This is a natural resource dataset so it is not as clean cut as other...
  19. trinker

    Assumptions of statistic models

    I was watching [Hadley's dplyr video]( and he said a statement that made me think: 8SGif63VW6E#t=134 I asked for clarification via Twitter and he said: I'm curious what others think about these comments. Do people agree? Is he saying the model...
  20. D

    Random Sample Assumption Violation and Chi-Square/Reg: Ordinal and Nominal Data

    Hello Everyone, I'm a grad student in biostatistics and am currently working at my first job with real world data. I'm analyzing survey data accessing employee's comfort with their work environment (DV) by several characteristics (IVs) (e.g., sex, race, religion). The DV, Comfort, is...