Questions tagged [adjustment]

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Adjusting alpha for several models in which I am just using most variables to adjust

If I have a study in which I run four regression models, each containing 5 independent variables, this would result in 5*4 = 20 p-values. However, let's say the first variable is what I predict has an ...
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1answer
20 views

P-value adjustment for different classes each tested individually

Testing the effect of a certain gene on survival of two different but somehow related (brain cancer GBM and LGG) patients, with each cancer (GBM or LGG) having several subtypes, how should I adjust ...
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1answer
33 views

Why adjusting for randomization stratification factors in the model improves the precision of estimators for treatment effect?

I assume you will already get balanced treatment assignment within the randomization strata. Why would we still gain improvement in precision by adjusting for these factors in the model? Does not ...
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1answer
32 views

Should the choice of propensity score matching versus weighting depend on the degree of overlapping of PS distributions?

I heard some opinions that matching is no good since it excludes some subjects. However, if we use PS adjustment or PS inverse probability weighting, is there a requirement on the degree of ...
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6 views

Checking conditional effects under all categorical predictor levels

When using many predictors, especially categorical ones, there is a possibility of overfitting due to the remained small number of data points for analysis. Is there also a possibility to check ...
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1answer
11 views

Categorical predictor: difference between additive vs hierarchical adjusting

Let's assume that: we are interested in the effect of X1 on Y that our data suits well for hierarchical modelling different cities have different number of subjects in our data Additive model: ...
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1answer
21 views

DAG: are there situations where adjusting for mediators is reasonable?

One thing about DAGs keeps bugging me - are there situations where adjusting for mediators is reasonable? E.g. consider the experiment below, where a power-calculated sample of subjects participated ...
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25 views

When should I apply the correction to the p-values for multiple testing adjustment?

I was doing a t-test with R in order to check if the means of 2 groups of measurements of the mRNA produced by 5 genes (the two groups are different because of the time in which they have been ...
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12 views

Relation between adjusted variable and variable used to adjust

I am trying to understand if it is correct to look for relation between a variable that was adjusted and the variable used for this adjustment. I have the variable X(i) = P(i)/N(i) and want to look ...
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8 views

Q: Using splines just for adjusting a fixed level effect in a hierarchical model?

I am interested how the outcome variable differs between the regions. My model including "age" variable causes clearly amplified Y-variable conditional means. ...
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1answer
23 views

How to adjust for a categorical variable in a way that its levels have equal weight in regression? (predictions are not for the reference category)

I hope I am not asking a stupid question :) Model salary ~ social_club + town Data ...
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17 views

Using Multilevel Regression with Poststratification to Adjust for Known Differences Between Sample and Population

I’ve read about the use of multilevel regression with poststratification to adjust for known differences between a sample and a population (see here for example). However, MRP seems to really be used ...
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1answer
25 views

Confusion with adjusting: adding all predictors into one model or running multiple models

I generally understand quite well the idea of adjusting; however, the current study design is killing me. Despite hours and hours of thinking (and my head almost explode), I still don't know, which ...
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0answers
10 views

Area and time adjusted counts

In 2019 I went to a site and counted 4 species of birds. The size of the site was 130 hectares and I spent a total of 54 hours counting the birds. The peak counts of the 4 bird species are presented ...
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1answer
116 views

P-value correction for multiple testing using huge datasets

First of all I apologize without the question is very basic, I am taking my first steps in data science, statistics and bioinformatics. Data information We are evaluating the correlation (using the ...
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11 views

Adjusting for references in augumented block design

I'm analyzing phenotypic response of 400 plants split into four augumented blocks, with 10 reference plants in each block. Additionally I have a data for 200 out of 400 in a separate block (with 10 ...
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1answer
30 views

Not understanding adjusted p values with Holm's method. Highest value in series divided by 1

I'm finding an issue while adjusting p-values with Holm's method I cannot understand. It's not a problem in my actual data, but I would appreciate any help to understand the issue. To show the ...
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1answer
64 views

Is there any consensus on adjusting p-values for multiple tests?

I'm confused as to when adjustments for multiple tests need to be used. I'm an undergrad who's familiarising himself with stats, so apologies if my question sounds dumb, but I haven't found any ...
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16 views

Paired comparison of multiple variables, how/whether to adjust for multiplicity

I would like to ask for advice about which statistical test to use. I want to compare the control left and the treated right knees of the same 10 patients (n=10 per group, paired comparison). I did ...
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1answer
81 views

Multiplicity correction when using emtrends to see if slopes are different from 0

I have a relatively straightforward question but I haven't been able to find the answer. Consider this example: ...
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0answers
84 views

Can controlling for baseline in a regression with change scores be appropriate? (within-subjects design)

I ran a regression model with a change score (post minus pre manipulation) predicting my dependent variable. Initially, I thought it might be also interesting to control for the baseline score (pre ...
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0answers
8 views

When do I have to correct for multiple comparison when computing different mutiple regression models?

I' ve got a problem with my thesis. I use a set of 3 bloodbiomarkers plus age as a covariate to predict Marker of Functional Connectivity on the one hand and Structural Connectivity on the other hand. ...
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1answer
57 views

Why match if you have the control data already?

I had a question about matching. I understand the benefits of matching prior to conducting a study due to potential increases in statistical efficiency/ adjustment for confounders. Let's say you're ...
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37 views

Phenotypes adjusted by Fixed effects - How to adjust a Covariate - R

Using as an example this file: ...
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99 views

Adjust cumulative incidence function curve by multiple variables in competing risks?

I am calculating a Fine & Gray Model for a data set with competing risks present. I got all the coefficients and their p-values. I know it's possible to plot estimated cumulative incidence curves ...
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1answer
36 views

Comment on the change in p-value following adjustment for confounders

The Second Australian National Blood Pressure Study (ANBP2) was a prospective, randomised, open-labelled, blinded to endpoint (PROBE) trial of Angiotensin Converting Enzyme (ACE) inhibitors versus ...
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2answers
91 views

Adjust alpha when switching from one-tailed t-test to two-tailed

I started with a hypothesis that says e.g. A is larger than B which would usually call for a one-tailed t-test. But after acquiring the data it turns out that the effect seems to be contrary to my ...
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1answer
130 views

Matthews/Phi Coefficient on a 2x2 Contingency Table with Rare Positives

Suppose I want to measure the degree people like gold versus silver. For the sake of argument, let's say I have a contingency table like so: ...
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1answer
50 views

Do I need to correct for p-value when doing repeated ANOVA test?

We are investigating the relationship between smoking status and the hormone level. Smoking status is X(three-level) and the level of the hormones is Y(continuous variable). However, the smoking ...
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1answer
39 views

How to adjust a confounder in pre-post analyis

I have a paired-dataset of pre and post-surgery measurements of certain biomarkers. I have done a paired t-test to find if there is a difference in the levels of a biomarker, say x1, before and after ...
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1answer
17 views

Unadjusted rates vs. observed rates?

In poisson and negative binomial rate models, should the observed rate be the same as the unadjusted rate (in model with only 1 variable)? Should you report these unadjusted rates from a model with ...
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0answers
38 views

'hold constant' and 'adjust for', do these terms have the same meaning?

In the context of regression, is there a difference between saying you held x constant and saying you adjusted for x? Or are these exactly the same thing? Thank you!
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92 views

How to adjust P values for several Post Hoc tests

I have several continuous dependent variables x1,x2,x3, and one categorical independent variable x4 with 4 levels, I want to apply ANOVA for each of these dependent variables one by one and then do ...
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1answer
31 views

Ideal method for confounder adjustment

I have a fairly large dataset (15,000) in which I assessed the association of a three-level categorical risk factor to the outcome. The outcomes were significantly different for the three levels. ...
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1answer
390 views

Multiple minimally sufficient adjustment sets in a Directed Acyclic Graph (DAG): Which unbiased estimate should be presented?

Assume that you want to estimate the effect of $X$ (exposure) on $Y$ (outcome). A common question is: What variables should we adjust for in our model in order to get an unbiased estimate of the ...
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23 views

Data normalization (reward/penalization) in a learning paradigm

wondering if folks can offer guidance on this data normalization problem. When trying to determine retention of information after a time delay, the retention rate needs to be adjusted for # of items ...
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0answers
28 views

Need of p-value adjustment when analyzing all possible pairs of factor levels in linear model

I have a nominal (not ordinal) variable with $K$ levels (these are actualy some groups of patients) and I run linear model in which: this nominal variable is one of IV's (others are age, sex and so ...
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1answer
61 views

Using binary outcome variables in real-world data studies must be wrong?

Please be gentle if it's a stupid(ly easy) question: In medical literature lot's of randomised clinical trials use binary outcome variables, such as 90% reduction in Y, or Y<(a certain threshold). ...
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1answer
22 views

Known Correlation between predictors

I have two predictors and an outcome, let's call them x, y and z. I know that x and y are correlated with correlation r. I am trying to construct a linear model: z = ax + by + c I have an ...
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26 views

Highly significant t-test statistics, any way to correct this?

I have been performing several paired t-test, where I test whether the sample means are different between two groups. For all of my tests (approx. 30), which all carries 13-14,000 observations, I ...
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2answers
444 views

Should all adjustments be random effects in a mixed linear effect?

I've been sometimes taught that when you are performing a mixed model, any variable of which you don't care about estimating a parameter (adjusment variable) should be a random effect, regardless of ...
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1answer
288 views

Significance of correlation with range restriction in x

Background Range restriction can happen in various study designs and it affects the results of bivariate correlation or in multiple regression, for example. In some cases the range restriction may be ...
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1answer
119 views

Deriving the values of the range around the mean value

This is part of a bigger quantitative reasoning assignment I was working on. My understanding here is that the upper bound and lower bound of the ranges for each of the exercises should be reflected ...
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2answers
773 views

How to calculate Mean adjusted by Covariate?

I need to calculate the mean of a variable, adjusted by another variable. Both variables are ratio scaled. I found this online: https://ideas.repec.org/c/boc/bocode/s344803.html which does what I want,...
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1answer
183 views

Adjust ROC analysis for multiple testing?

we did an exploratory prospective study in medicine in order to find parameters which are able to predict a specific post-surgical event (0/1) before the actual surgery. We have about 10 parameters ...
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1answer
480 views

How to do a survival curve adjusted to age in SPSS? [closed]

I have to do a survival curve comparing 3 diseases. Already did a Kaplan Meier since time of diagnosis, and the log rank was p-0.001; however I suspect that it has to do with age (one disease is ...
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0answers
24 views

Adjust two coordinates based on the distance between them [closed]

I have two positions $\overline{X_1} \in \mathbb{R}^{2}$, $\overline{X_2}\in \mathbb{R}^{2}$ with the respectively measurement errors $\Sigma_{X_1}\in \mathbb{R}^{2\times 2}$ and $\Sigma_{X_2} \in \...
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1answer
29 views

Is this a valid method to adjust for multiple testing?

Assuming I have 100 variables and I do a t-test for each of them without adjusting the p-values, and get 8 significant p-values out of the 100 tests. If my alpha is 5% can I just say that since I ...
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0answers
148 views

Statistical adjustment for regression

I already checked out the answer to this: enter link description here It is not a duplicate and that did not answer my question. I wanted to try to ask a different question regarding a similar ...
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28 views

P value adjustments when subsetting dataframe

I'm analysing a dataset that contains different species. I first use the species ID as an independent variable but then I have to analyse the dataset separated for the different species (in total 3). ...