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0
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1answer
14 views

Change over time controlling for size of start point

I have some data on a group of people. The data look like these (each column is separated by a comma, values in top row are variable names, the dataset has c100 rows in total): ...
0
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0answers
25 views

how do we know if interaction effect exist between two continuous variables

I have a dependent variable (y) and three independent variables X1, X2, and X3. The correlation table shows that each of these independent variables has significant positive relationship with Y. But ...
0
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0answers
12 views

Continious to discrete state space modeling

Does anyone has Matlab code to convert continuous state space model to discrete domain symbolically based on parameters.My A matrix has 12x12 symbolic variables and getting exp(A*T) for discrete A is ...
4
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1answer
181 views

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 ...
1
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0answers
35 views

Estimating prevalence of an effect in a RCT study using the overlapping coefficient (and does chocolate make your acne worse?)

I'm trying to tease out prevalence of effects seen from controlled studies, e.g. what % of people would expect to see a higher acne lesion count if consuming 6 oz of cocoa / day? The average effect is ...
7
votes
1answer
276 views

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 ...
0
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0answers
31 views

How to use controls as a reference in GLM?

I'm running glms in R on two datasets, both with three discrete explanatory variables and one continuous dependent variable. My question is about the use of controls - I want to use my controls as a ...
1
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0answers
15 views

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 ...
0
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0answers
8 views

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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0answers
3 views

Selecting control locations for tiered groups?

I have groups of locations categorized by their sales performance and weekly variability into four tiers. We are running on-site tests for 100 locations in Tier A against a set of 50 control locations ...
2
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2answers
39 views

How to select a control / comparison group?

Lets say I'm creating a study that looked at treatments for metastasis in African American colon cancer patients. Would my control group or comparison group be Caucasian colon cancer patients with ...
0
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0answers
20 views

Should I run Hierarchical regression to test moderation? Why?

I am an undergraduate student who currently preparing for my thesis paper. In my design, there is total 4 variable (1 predictor, 1 moderator and 1 outcome variable, all of them is in continuous ...
0
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0answers
30 views

SAS syntax to find differences in regards to a control treatment

I am working with a data set of bacterial cell counts, using flow cytometry. I recorded the cell number in 3 different species of bacteria, all treated with 3 different compounds (L-aspartic acid, ...
2
votes
2answers
947 views

What is “the” correct way of calculating Cp/Cpk values for Statistical Process Control?

There seems to be many different methods of calculating Cp/Cpk values in SPC, and I need help in determining which one to use at any given situation. Currently, we need to show Cp/Cpk values when ...
-1
votes
1answer
79 views

what to do if all control variables are insignificant and none affect the main effects?

All the control variables were there because they affected the dependent variables in previous studies. However in my dataset, all are insignificant and do not affect the main effects. Should I ...
1
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0answers
35 views

Estimating a first order plus dead time model

The data generating process is given by the following differential equation: $y(t) = a + b u(t - \theta) + c \frac {dy} {dt}$ Now imagine having as data a long time series for both $y$ and $u$. If ...
0
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0answers
148 views

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 ...
1
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0answers
63 views

Do significant control variables need to be eliminated from statistical analysis in general and SmartPLS specificly?

I have been told that we need to eliminate control factors that shows a significant impact on the dependent variable from the model. As I know that control variables are variables that have testified ...
0
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0answers
19 views

Can Cramér's V tell me what to control for in my data?

For my research question, I want to find out if two different group types (IV) vary across position categories (DV) for eight different limbs. My data is nominal, so I'll be testing this by doing 8 ...
2
votes
1answer
108 views

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 ...
1
vote
1answer
69 views

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 ...
1
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0answers
15 views

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 ...
2
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0answers
151 views

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 ...
3
votes
1answer
281 views

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 ...
2
votes
2answers
59 views

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 ...
1
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0answers
37 views

Siginificant size for a Control Group

I am designing project which requires me to select a Control Group. One the business requirements stipulates that I select as small a sample size as possible for the Control Group so there will be ...
1
vote
0answers
37 views

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 ...
1
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0answers
29 views

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 ...
1
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2answers
168 views

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 ...
14
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3answers
1k views

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 ...
4
votes
1answer
192 views

Proportion as Dependent Variable or Control for the Denominator in Regression Model

I am a little confused as to which model specifications to use for my question. I have number of technological failures (positive count variable) as dependent variable but I am supposed to control ...
4
votes
2answers
70 views

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 ...
4
votes
1answer
360 views

How do you “control” for a factor/variable?

To my understanding, "Control" can have two meanings in statistics. Control group: In an experiment, no treatment is given to the member of the control group. Ex: Placebo vs Drug: You give drugs to ...
3
votes
2answers
285 views

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, ...
1
vote
1answer
182 views

Statistical test for normalised data

I am working with culture cells where one dish has been transfected with a scrambled knockdown clone and two dishes which have been transfected with two knockdown clones each knocking down the ...
5
votes
3answers
307 views

How high must logistic covariates' predictive accuracy be for a reversal effect to show up?

I am modeling an outcome for hospital patients, 'RA' (whether readmitted; 0=No, 1=Yes). My predictor of interest is 'HHS' (whether referred to Home Health Services such as from a visiting nurse; ...
1
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0answers
50 views

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 ...
1
vote
1answer
2k views

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 ...
2
votes
1answer
205 views

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 ...
2
votes
1answer
169 views

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 ...
0
votes
0answers
109 views

Too many controls?

I am purposely keeping this question vague since this has happened to me with multiple datasets. I have a DV and a few IV then several controls, and all looks fine. Then I add one more controls and ...
0
votes
1answer
154 views

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) ...
0
votes
2answers
60 views

How to determine influence of two time series with feedback?

Say you have two time series, A & B. Each have a mutual effect on the other. To give a real-world example, say that time series A measures an artist's CD sales per month, and time series B is some ...
1
vote
1answer
153 views

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 ...
1
vote
1answer
532 views

What if only control variables are significant in a differences-in-differences analysis?

Regarding the standard DID model: $$ y=\alpha+\beta_1\text{treat}+\beta_2\text{post}+\beta_3\text{treatâ‹…post}+u $$ What exactly does it mean if say $\beta_3$ is not statistically significant, but ...
8
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3answers
153 views

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 ...
0
votes
1answer
184 views

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 ...
5
votes
3answers
1k views

How to control for market return in an (SPSS) OLS?

Please consider the following panel dataset: ...
1
vote
1answer
293 views

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 ...