Centering involves subtracting the overall sample mean score from the original score; standardizing does the same followed by dividing by the overall sample standard deviation.

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2answers
61 views

Between-subjects effect becomes non-signicant after centering covariate. Should I center or not?

I've used a general linear model function to run an ANCOVA, involving a categorical predictor (with two levels), a continuous predictor, and their interaction effect. If I don't center the ...
0
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0answers
12 views

When should one centre variables in a cox proportional hazard model and when not? [duplicate]

I want to use a Cox proportional hazard model in order to analyze the prognostic value of a certain variable (I divided it in quartiles and so I have 4 categories) with respect to the time to event ...
0
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0answers
21 views

Is scaling data valid for Kruskal-Wallis test?

I have a dataset of fresh matter (FM) weights of salad measured in field over time (6 Dates, 40 Plants each). Those are measured independently, so at every date different plants were measured. As in ...
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1answer
23 views

Which mean to use for centering variables when sample definition varies

I am centering variables that enter interaction terms in my linear regression. To check the robustness of my results, I exclude certain cases from the original sample, and re-run the regression ...
8
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3answers
235 views

How to include $x$ and $x^2$ into regression, and whether to center them?

I want to include the term $x$ and its square $x^2$ (predictor variables) into a regression because I assume that low values of $x$ have a positive effect on the dependent variable and high values ...
0
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1answer
98 views

Do you ever center AND standardize variables in multiple regression?

Do you ever center AND standardize variables in multiple regression? It seems as if standardization would automatically center variables...is this true?
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0answers
37 views

Which mean centering approach is correct?

I have 2 possible ways to mean center. Take the mean of the training data only, and center both test and training data using it. Take the mean of combined test and training data, and center both ...
3
votes
3answers
537 views

Is centering a valid solution for multicollinearity?

Let's assume that $y = a + a_1x_1 + a_2x_2 + a_3x_3 + e$ where $x_1$ and $x_2$ both are indexes both range from $0-10$ where $0$ is the minimum and $10$ is the maximum. I found by applying VIF, CI and ...
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0answers
34 views

Centering variables before running PCA [duplicate]

I am learning about PCA, regarding PCA I need to know that given a dataset is it always necessary to use centering? what if I don't center the variables used in PCA?
0
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0answers
391 views

How does knnimpute of the preprocess function work?

I am new to R and I use a script I do not completely understand. It preprocesses a dataset for data mining. At one point, the data (stored in fil) should be ...
1
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1answer
530 views

Centering data in multiple regression

In a multiple regression analysis (with 4 continuous predictors and 2 categorical factors), we mean centered the data (for each continuous variable) due to issues of multicollinearity when the ...
2
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0answers
133 views

Which variables should I transform, center, and/or standardize in my data for Principal Component Analysis?

I have multiple datasets that I am attempting to use principal component analysis (PCA) on in order to infer the underlying structure of the data. I'm attempting to predict growth increment of ...
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2answers
57 views

Does it make sense to partially scale the data matrix X in regression?

For some reason my supervisor wants me to centre only the independent variables that are used in interaction terms. I have never heard of such a practice. Does it make sense to partially centre data ...
3
votes
1answer
981 views

Converting standardized betas back to original variables

I realise this is probably a very simple question but after searching I can't find the answer I am looking for. I have a problem where I need to standardize the variables run the (ridge regression) ...
3
votes
0answers
71 views

Should I de-mean a predictor variable before a dummy interaction

Suppose I have the following time-series linear model where $\beta$ is misspecified: $Y(t+1) = \alpha + \beta X(t) + \sum_{i=1}^{10000}\gamma_i Z_i(T) + \varepsilon$ where all parameters are in ...
7
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2answers
615 views

How to include a linear and quadratic term when also including interaction with those variables?

When adding a numeric predictor with categorical predictors and their interactions, it is usually considered necessary to center the variables at 0 beforehand. The reasoning is that the main effects ...
1
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2answers
121 views

Centering when using splines in R

I am having trouble understanding why centering seems to only work with simple linear models and not with splines for example. I am using centering to report the estimated group differences at ...
2
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0answers
120 views

Interaction Term Insignificant but Composite Variable Significant

I have 4 latent variables each with 3-7 indicators. I created a composite for each variable by summing the data and then mean-centering (variables have some collinearity issues, highly related). ...
4
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0answers
116 views

How to do centering if I have a quadratic term?

I have been trying to run a multilevel model with both a linear and a quadratic term for income as my main variables of interest. It looks something like: \begin{eqnarray} ...
0
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1answer
58 views

How to determine the best mean to use for a developmental comparison using z-scores?

The data contains two groups and the intended comparison will be completed via independent t-test. Options that I have considered is using the entire sample's mean or one of the group means. However, ...
8
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2answers
3k views

Why could centering independent variables change the main effects with moderation?

I have a question related to multiple regression and interaction, inspired by this CV thread: Interaction term using centered variables hierarchical regression analysis? What variables should we ...
5
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1answer
2k views

Interaction term using centered variables hierarchical regression analysis? What variables should we center?

I'm running a hierarchical regression analysis and I have some little doubts: Do we calculate the interaction term using the centered variables? Do we have to center ALL the continuous variables we ...
6
votes
1answer
372 views

Should I re-center variables when looking at moderator effect in men and women separately?

I want to see if an interaction variable in a multiple regression is significant for the whole sample, and then just for men and just for women. When I created the interaction variable for the whole ...
3
votes
1answer
73 views

Convert back standardized linear predictor

I guess this is a quite basic question, but I have been struggling with this for quite some time, so I hope someone can help me with this. I have a model (type is not relevant for now) which includes ...
3
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0answers
149 views

Interpretation of interaction term in Cox PH model when centering LP on mean values of predictors

Let's say I have a Cox PH model for predicting the risk of dying, that in a simplified form looks something like this: ...
0
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0answers
122 views

GEE: Pairwise comparisons at different levels of a covariate?

I'm familiar with basic regression methods, but have no experience using GEEs. I use SPSS, and I'm trying to use a GEE for a dataset that I have, because there is a repeated measures component in my ...
2
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0answers
63 views

Few main variables in the best model still show multicollineairty. Should I remove them despite their importance?

I have a binary logistic regression with 5 IVs and all of their 2-way interactions. I have reduced/removed multicollinearity between main variables and their interactions by centering the main ...
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1answer
161 views

After centering, interactions' effects got reversed. It was not fixed by reversing the dependent variable. What should I do?

In a binary logistic regression, I centered all the independent variables (binaries, continuous, dependent, independent, all [I have 5 IVs: three binary and two ordinal]). Multicollineariy was ...
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0answers
48 views

Centering to use a sparse covariate?

In my dataset, there's a binary response, some factors, and some covariates. In particular, there are some covariates that are always present when factor1=="A" and ...
11
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1answer
464 views

Is centering needed when bootstrapping the sample mean?

When reading about how to approximate the distribution of the sample mean I came across the nonparametric bootstrap method. Apparently one can approximate the distribution of $\bar{X}_n-\mu$ by the ...
4
votes
1answer
385 views

Shifting bootstrap confidence interval to be centered around original parameter

I've been doing a bit of research into bootstrapping as I've been told one method of performing it, and this seems to differ from what I can find in other sources. I have a sample, and want to ...
61
votes
8answers
45k views

When should you center your data & when should you standardize?

In some literature, I have read that a regression with multiple explanatory variables, if in different units, needed to be standardized. (Standardizing consists in subtracting the mean and dividing ...
15
votes
1answer
2k views

How does centering the data get rid of the intercept in regression and PCA?

I keep reading about instances where we center the data (e.g., with regularization or PCA) in order to remove the intercept (as mentioned in this question). I know it's simple, but I'm having a hard ...
5
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4answers
6k views

How to group-center / standardize variables in R?

Functions I'm familiar with include scale from base R, rescale from ARM. Perhaps the best way would be to use some variant of apply, specifying one or more variables to use as grouping variables.