multivariate analysis

I have a group of organisms to which I apply a number of treatments (N). For half of the organisms to which I apply a treatment, I measure response y1 (effect) and for the other half I measure response y2 (control). Part of the responses later appear invalid and are discarded, resulting in...

Hi, I have 18 variables (soil biogeochemical properties) that I want to put through a PCA. Some variables have large units (e.g. %) and some small (e.g. mg C/L). Should I transform the larger units before running them through PCA? Some of the variables also have non-normal data; should I also...

Hi everyone, I have the attached multivariate mixed model in matrix notations. I have been advised to use tensor notations to simplify the model formulation in the multivariate case. Since, I am unfamiliar with the tensor notations, I looked at different online resources but I get lost very...

I'm trying to tabulate some concentrations of compounds to eventually test if tide (or depth for other samples) and distance along a sampling transect affect these compounds (the 5 variables on the right). However, the only way I can think to do this is in the attached image, where I'm forced to...

I have a question about multiple regression. May I kindly ask how should I interpret the conditional main effect when the interaction is 0 and the coefficients have opposite signs, more specifically if one of the interaction term contains zero such as angle or time. Please see an example...

I am studying the difference between STRESS and SSTRESS optimization functions in the context of multidimensional scaling. I have encountered this definition of optimization criteria for the SSTRESS: My question is : why using squared estimators and squared distances (in MDS or in general)...

Hello! I have several count values for two groups in several variables, as seen on the plot. I have seven observations in the purple group and 74 in the grey group. I have 10 variables (x axis). I want to compare the distributions of the purple and grey groups in each of the 10 variables. I...

I am not sure if I should run MONOVA or some other test? I have collected data from two different sample groups. I have one categorical and two continuous dependent variables + one categorical independent variable. Because of the continuous dependent variables, I'm not too sure about using...

I am doing research to predict if alcoholism is an independent risk factor for bleeding after surgery. I will perform a univariate analysis with a chi squared test to know if other factors, such as age, sex, comorbidities,... are associated with an increased risk for postoperative bleeding...

Hello all and thanks for any future responses. I am doing a study looking at whether three independent categorical/dichotomous variables (gender, Greek status, and class status (i.e. freshman vs senior)) influence a person's disordered eating behaviors and attitudes among college students...

Hi, I am writing my thesis for medicine about postoperative complications of a disease (IBD). The dependent variable in this case is whether the patients had a post-operative complication or not (binary) within 30 days of their operation. The sample size for my study is n = 62. I have...

Hi there. This will be my first post on the forums, I'm a Psychology student currently conducting research at an internship. We treat IDD (Intellectual Developmental Disorder) patients with different types of therapy, and I've been assigned to study the dosage components of DBT (Dialectic...

I have 7 subscales/dependent variables and I want to find the relationship/effect of 1 two-group qualitative variable, a quantitative covariate, and their interaction on those 7 DVs. I ran 7 hierarchical regressions (with the interaction in block 2), and 7 ANCOVAs to test these and in all cases...

Hi all, I have a data set with 3 proposed dichotomous independent variables: sex (male or female), side (left or right), and region (lower or upper). I want to know which are significant / affect my dependent variable: distance. Apparently, in the medical research community, it is common to...

Hello everyone! I just started modelling and I have a question about how to interpret my results. I built 3 models, two univatiates (Z ~ bX + e; Y ~ bX + e) and one multivariate model ( Z, Y ~ bX + e). In both univariate models 'X' was not relates with 'Z' or 'Y', but it was in the...

Hi all, I'm interested in the potential effects of water pollution on feather color of a bird. For this, I calculated 4 color variables for each individual (brightness, hue, blue chroma and UV chroma), which are my 4 dependent variables. My independent variables (explanatory) are the...

The same participants are exposed to two different screen sizes 27" (stimulus A) and screen size 9.7" (stimulus B). Independent var is "screen" with two levels - sizes. After exposure to stimulus A, they fill two questionnaires to answer dependent variables Y1 and Y2. After that, they are...

Dear all, I have the following biological data: 1st variable (continuous, normally distributed): concentration of a hormone in blood 2nd variable (continuous): age of donors 3rd variable (categorical): genotype (control vs mutation-carrier) 4th variable (categorical): gender (male vs...

Let, \mathbf y_i = \mathbf X_i\mathbf\beta + \mathbf Z_i\mathbf b_i+ \mathbf\epsilon_i, where \mathbf y_i\sim N(\mathbf X_i\mathbf\beta, \Sigma_i=\sigma^2\mathbf I_{n_i}+\mathbf Z_i \mathbf G\mathbf Z_i'), \mathbf b_i\sim N(\mathbf 0, \mathbf G), \mathbf\epsilon_i\sim N(\mathbf 0...

Let \mathbf x is a (p\times 1) vector, \mathbf\mu_1 is a (p\times 1) vector, \mathbf\mu_2 is a (p\times 1) vector, and \Sigma is a (p\times p) matrix. Now I have to show -\frac{1}{2}(\mathbf x-\mathbf\mu_1)'\Sigma^{-1}(\mathbf x-\mathbf\mu_1)+\frac{1}{2}(\mathbf...