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12 views

removing the effect of a categorical variable in a linear model

I would like to remove the effect of a categorical variable from a linear regression model. A simple example could be the following: outcome ~ beta0 + beta1 * dummyIsFemale + beta2 * ...
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0answers
14 views

Measuring training effectiveness

I am measuring training effectiveness using a control and experiment group design. However, as it is a live project in an organization having an 'interest based' approach for training subscriptions, I ...
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0answers
12 views

Omitted Variable Bias Formula - Regression Interpretation

In the book "Masterin' Metrics" on page 136, they are discussing instrumental variables. In this specific application, they are using a twin births to instrument family size in an attempt to obtain a ...
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1answer
40 views

Controlling for age and sex in a multiple regression with a backward model selection

So, I have this dataset with a hormonal measure as independent variable and behavioral measures as dependent variables. I am using a linear regression as my model and after a backward selection, ended ...
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0answers
35 views

Q: How to correctly include a categorial control variable in a regression model (in R)?

I'm trying to fit a (logistic) regression model to predict the successful funding of crowdfunding ventures (0/1) based on a series of IV with different level of measurement. One of these IVs is a ...
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0answers
20 views

“Controlling” for population/sample sizes when looking at rates?

I have a pretty basic understanding of statistics, so please bear with me: I'm making an index (ranking) of sector performance I am including indicators such as "Percent of profitable firms in ...
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0answers
11 views

Conditioning on random effects?

To protect the innocent, I'm going to fabricate an example. Suppose I've got 100 musicians: 50 attended school A, 50 attended school B. I'm interested in determining which school tends to produce ...
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2answers
101 views

Best statistics to show outliers beyond 2 SD

I try to perform scheduling for an organization based on client flows. We are very seasonal. Our senior management in Washington, DC make us base our schedule on the mean number of clients we have ...
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0answers
30 views

In two places at once: treatment and control groups

When performing a treatment study (e.g. a difference-in-differences design) in multi-dimensional panel data (e.g., firm-individual-time, bank-firm-time, etc.) is it ok if the "smaller" cross-sectional ...
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0answers
87 views

propensity score matching and difference in difference

I am trying to analyse the impact of a cash stipend program, onto child learning outcomes. I have first modeled the conditional probability of each student receiving this program. So basically I have ...
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1answer
55 views

Logistic Regression- Control Variable Not significant In Model 2

I am new to this site and it's my first post, so my apologies in advance if I have made any mistakes or did not follow proper etiquette. I am running a logistic regression analysis with six predictor ...
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0answers
26 views

psychic testing control group

You have seen it on television, two men sit across a table from each other, a deck of cards between them. The man in a lab coat draws a card and looks at the card. The other man places his hand to his ...
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0answers
28 views

Comparing Binomial Success Parameters in a Stratified Approach - An Example in Biostatistics

I would like to contrast the effectiveness of drug treatment and surgical treatment in a study with the following data. Each row represents one trial, and each trial uses either drugs or surgeries to ...
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0answers
34 views

Control chart constants [closed]

When calculating Upper Control Limit (UCL) and Lower Control Limit (LCL) in control charts I use constants from ...
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1answer
48 views

How to analyze this pre-post control-intervention data set?

I have control and intervention groups (N = 50 and 75, respectively) for whom 15 tests (all having quantitative results) were done at baseline and at 3 months. It is not a randomized study and the ...
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0answers
34 views

Subset items from a group while controlling for variables between groups

Can anyone offer solutions to the following problem?: I'm trying to extract a subset of items from multiple groups (grouped by 2 separate factors) so that the final groups are: 1) of equal size, and ...
0
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1answer
146 views

How to calculate critical values for Dunnett procedure given alpha, df1 and df2

I am looking for an R function that can calculate critical values for a Dunnett multiple comparison procedure for any family-wise error rate and degrees of freedoms. In short, I need similar ...
2
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1answer
19 views

Use of words “control” and “test”

There are 2 groups of people, group A and group B. The groups were NOT assigned randomly and are not the same size. It is true that group B has a higher rate of success than group A, but this was ...
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): ...
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0answers
41 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 ...
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0answers
51 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 ...
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1answer
211 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 ...
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0answers
46 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 ...
8
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1answer
346 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 ...
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0answers
40 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 ...
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0answers
17 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 ...
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0answers
11 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
5 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 ...
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2answers
50 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 ...
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0answers
36 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 ...
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0answers
58 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
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2answers
4k 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
148 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 ...
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0answers
42 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 ...
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0answers
104 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 ...
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1answer
232 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 ...
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1answer
122 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 ...
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0answers
19 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
268 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
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1answer
586 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
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2answers
113 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 ...
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0answers
47 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
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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
32 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
210 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 ...
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3answers
2k 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
2answers
258 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
73 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
675 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
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2answers
430 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, ...