# Tagged Questions

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### What does “all else equal” mean in multiple regression?

When we do multiple regressions and say we are looking at the average change in the $y$ variable for a change in an $x$ variable, holding all other variables constant, what values are we holding the ...
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### What is the link between methods such as matching and statistically controlling for variables?

Often in research articles you read the researchers have controlled for certain variables. This can be done by methods such as matching, blocking, etc. But I always thought controlling for variables ...
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### What is the difference between controlling for a variable in a regression model vs. controlling for a variable in your study design?

I imagine that controlling for a variable in your study design is more effective at reducing error than controlling for it post-hoc in your regression model. Would someone mind explaining formally ...
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### How to control for market return in an (SPSS) OLS?

Please consider the following panel dataset: ...
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### Choosing Location Based Control Group

I have a dataset that tracks activities at particular locations. The dataset is essentially, timestamp, latitude and longitude, indicating an activity at that lat-long and that time. I plan on ...
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### How can I calculate the effect of my equipment on my sport's performance?

I'm doing a stationary sport like golf, so the details matter. I'm recording each of my scores with detailed information about the equipment I'm using, and the weather conditions. So 1 score has 2-3 ...
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### How are partial regression slopes calculated in multiple regression?

I'm trying to understand how multiple regression statistically controls for the effects of other predictor variables when calculating partial regression slopes. In a multiple regression of Y~X1+X2, ...
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### How to explain control variables and interaction effects

I'm a bit stuck on running a GLM between 3 continuous variables in R. I can't make them categorical as it removes the significance. I have two questions. I'm analysing data on eggs. I had read that ...
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### Balancing gender in an experiment

Say a study aims to see if two variables A and B are correlated in the general population. It isn't clear to me how extraneous variables like gender should be treated when the sample is selected. Each ...
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### Pros and cons of controlling for age when examining effect of cognition on driving performance

I am reviewing some studies on the relationship between cognition and driving. Some studies have controlled for age and some have not (age is correlated with cognition. Can anyone please provide any ...
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### Control limits in $\bar{x}$ and R chart

I am learning a Quality Control course and in theory part I don't understand calculating the control limits for $\bar{x}$ and R chart.I want to know, say when I calculate the R chart control limits no ...
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### Using control variables in Difference in Difference method

When random experiments are conducted, 'baseline data' are usually used as control variables in order to increase precision. How about control variables in Difference in Difference method? What I ...
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### Quality Control Chart for non-normal distributed data

I am interested in building quality control charts for time series data where every data point has different gradation within the range of 0 to 1. For example first data point X1 may be 0.1, 0.2,..,1 ...
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### How to control for a variable

The goal of the analysis is to find a correlation between birth context and stature, while controlling for age. Each person has an ID number, age, stature, and birth context. That last part is what ...
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### How does my questionnaire analysis plan sound?

I will soon have the results of a questionnaire that I have carried out, and I have made a plan on how I will analyse the data. I was hoping that someone could comment on my plan to advise me. About ...
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### Covariates considered moderator or control variables?

Are covariates considered moderator variables or control variables? To elaborate on my question, I'm conducting a research study which has: variables that are supposed to affect the dependent ...
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### How to determine the correlation between 2 time series while controlling for a 3rd?

I would like to determine the relationship between two variables after controlling for a third. Specifically, I want to know if the prices of mercury and gold over time are correlated with each other ...
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### What if only control variables are significant in a differences-in-differences analysis?

Regarding the standard DID model: $$y=\alpha+\beta_1\text{treat}+\beta_2\text{post}+\beta_3\text{treat⋅post}+u$$ What exactly does it mean if say $\beta_3$ is not statistically significant, but ...
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### Dividing controls between two groups of cases

I have a set of data that contains cases and controls. I would like to divide the cases by a particular phenotype before running my tests, to see how these groups differ (but not necessarily to ...
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### Interpreting Omitted Variables

I do not fully understand how to interpret the difference between two statistical models where they only differ based on whether a certain variable is included on the right hand side. If the results ...
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### Help required in controlling for socioeconomic factors when mapping travel behavior

Background I have cleaned disaggregate travel data down to a household level (of about 75% of households) and socio economic data aggregated into 100-200 household blocks. What I'm wanting to do is ...
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### Scale of control variable in ANCOVA

I am new to the field of ANCOVAs. I want to check if two groups differ in three quantitative variables. At the same time I would like to control for gender and diagnose (6 categories). Is it ...
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### How to assess whether IQ predicts emotional experiment more at time 1 or time 2 controlling for covariates?

I have the following data set of a two-wave longitudinal study in educational psychology. A group of 400 people did some questionnaire on IQ, personality and two different emotional states (sadness ...
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### Controlling for respondents' propensity to rate high/low or moderate/extreme

I am doing a simple linear regression to test the relationship between voters' self-reported policy stands and their approval ratings for two hypothetical presidential candidates in a simulated ...
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### Unexpected correlation, Method to account for the shared variance

Summary: While looking at the correlations I noticed a wired, relation. Variables: User comments - A; User community activity- B; Comments on user's wall - C (control) I expected that A and B will ...
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### Partial correlation

I want to create a regression model to predict state crime rate. There are two variables among 10 ( Vi= # of violent crimes per 100,000 population, Vi2 = # of violent crimes per 10,000 population) ...
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### controlling for a highly correlated variable

In a paper looking at hand movements and time taken to complete a task it appears that the ratio of movements over time is constant (i.e., movement and time are highly correlated) yet they say in the ...
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### For industrial statistical process with sparse data, what is the maximum allowable sparseness?

Suppose you have a factory that does statistical process control by randomly selecting workpieces and measuring them. Suppose you've got 1000 workpieces in a month, and each piece starts as raw ...
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### multivariate control chart

I am trying to build a multivariate control chart but I did not find any good explanation of how to do that. Starting with $x_0$ a part of the samples that are in control I compute $\mu_0$ and ...
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### Numerical optimization of Bellman equations for stochastic dynamic programming problems

I am trying to carry out the discretized process suggested by the authors in this paper, i.e. the numerical optimization, and would be grateful for some pseudo code or better still R code that might ...
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### Common or regional time dummies as controls: Does it make a difference?

I am analyzing policy diffusion using panel data, and the inclusion of temporal controls substantially influences my results. I'm wondering if it can theoretically make a difference for the estimates ...