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9 views

How to interpret linear regression with different categorical variables

I am looking at the effect of 1 categorical dependent variable A (3 outcomes) on 1 independent variable. This is significant. Then I want to see if this effect is still true if I add another ...
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0answers
20 views

Control group construction in Synthetic Control Method

I want to use the Synthetic Control Method to estimate the effect of the adaption of a new ballot institution (treatment) on fiscal policy. My sample consists of 20 units observed at 100 time points. ...
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20 views

Difference in difference with pre and post period

I wanted some guidance on some test I am performing. Basically I want to see the difference between the effect of unionisation on 13 countries grouped into 3 that don't have unions and 10 that have ...
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1answer
44 views

Controlling for biased audiences in online surveys

For a long time I have been meaning to set up a bunch of online surveys asking a whole range of social questions and publish the results. I am well aware that there are various difficulties to ...
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1answer
26 views

Gradient descent for a noisy system

I have a system with tuning parameter $w$. To evaluate this system I use cost function $f(w)$. I try finding the optimum value for $w$ using Gradient Descent starting from $w_0$. The problem with ...
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0answers
15 views

Using control charts with very large subgroup size?

I am working with a very large data set -- time-series data from an on-line process monitor with a 10 second measurement interval. I am trying to develop control limits for the process using control ...
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0answers
17 views

Can Control Variables also be included as Dependent Variables?

I'm currently reading an academic journal (http://papers.ssrn.com/sol3/papers.cfm?abstract_id=2488863) which, in Table 11 of the paper, lists several control variables including: Returns Size ...
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0answers
8 views

Control of assumptions in general linear model

In which ways can I "control" the assumptions I make in a linear model where I have $n$ independent, random variables with same variance and where the mean vector lies in some subspace (a strict ...
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2answers
54 views

“Controlling” for multiple sequential association rules?

Assume I have data along the following lines A-A-B-C A-A-B-C A-A-B-C Then I test the following sequential association rule: "A-A precedes C", which is true 100% ...
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27 views

Determining minimum required sample size for control (for purposes of measuring lift)

SO in a sales setting where people can either buy or not buy (i.e. binary response), say I have a treatment that I know (or believe strongly) to be effective. I want to give it to as many people as ...
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0answers
26 views

Predictions in a control loop like airconditions

I wonder if there are special things to consider with predictions in a control loop, e.g. An airconditioner trys to hold the target temperature at 20 degrees. I want to predict the energy ...
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0answers
13 views

ANCOVA--Introduce second covariate

I am conducting a pretest-posttest ANCOVA with a control group in which I covary the pretest data and use the posttest data as the dependent (Jobs). Time is a repeated measure with 6 pretest and 9 ...
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0answers
22 views

Defining the size of control group in chi square statistics

I'm trying to compare the prevalence rate of autism in offspring of mothers with and without gestational diabetes. I gathered data from 1000 women, 8 children have autism (prevalence rate 8/1000). ...
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23 views

Should I control for categorical control variables that are related to my independent variable in panel with many panels, short time length?

I am doing a panel study where I have a sample of persons $i=1...N$ (up to $N=300$), that have some personality dimension quantified as variable $x$, over a time horizon $t=1...T$ (up to $T=20$). From ...
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0answers
36 views

Adding control variable to difference-in-difference equation

I'm new to this so bear with me. I'm running a Difference-in-Difference analysis, this is the equation: Yit = α+ β1Treati + β2Postt + β3 (Treat⋅Post)it + ϵit I want to control for a few variables, ...
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26 views

Should I check control variables for robustness?

I am working with count data and using a negative binomial regression. I have 3 core independent variables and control variables (age,education and sex). But the problem is that I have 8 age groups ...
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0answers
24 views

Is there a way to test whether or not you're “over-controlling?”

Just got a stats assignment back in which I was told that "many of these regressions are over-controlling." However, each one of the controls were independently statistically significant, so it's not ...
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0answers
41 views

Control Variables-Difference in Differences-Repeated Cross Sectional

I have a question regarding control variables in a difference in difference model with repeated cross-sectional data. Is it allowed to add individual level controls while you are looking at group ...
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0answers
22 views

Newbie question: can a categorical IV be included in ANCOVA with only a couple observations in 1 group

I think this is a pretty simple question, but I have been unable to find an appropriate answer. Please help. I have identified a sub-sample of my treatment group that were taking a medication that ...
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0answers
14 views

Estimating process standard deviation for a quality control chart. What is $s/(c4)$ and how to calculate it in R? [duplicate]

I recently came across quality control charts in my studies and found out that the estimator $$\hat \sigma =s/c4$$ is preferred for UCL and LCL calculations in an x bar chart as it is considered ...
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0answers
17 views

Determine Number of Users in Control and Treatment Groups

I need to be able to determine how many users should be in a control group and how many users should be in the treatment group. I have read that it is statistically best to split it 50/50, but with my ...
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1answer
42 views

Failure prediction from production line data/ Statistical process control

I'm a research student looking into predicting product defects from on-line time series data. I'm struggling to find exactly which statistics area I should be looking into to create an error ...
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25 views

Remove estimated effect of independent variable on dependent variables (interval/ratio) using linear regression

Question: Can we use unstandardized coefficients derived from linear regression to remove the effect of an independent variable on the dependent variable? I have a large dataset and suspect that an ...
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1answer
32 views

Control variables in experiments

Assume you are trying to test the effect of condition X. You sample people randomly and put them in a manipulation group (condition X) and a control group (condition Y). Simultaneously you want to ...
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0answers
9 views

Is there a unified form for Process control and process control analysis

I have done some reading (NIST, JMP, PCS, Juran, some JEDEC, ...) and it appears there are four very common general types of control charts: Shewhart (X-bar, R, S) CUSUM (cumulative sum) EWMA ...
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23 views

Which method should be adopted for pretest and posttest research?

My company will hold three types of activities (leisure, family-oriented and interest class) in order to improve the co-worker relationship. I am assigned to use questionnaires (by using the workplace ...
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0answers
25 views

Control Chart - Descriptive or Inferential?

Which category of statistics do Control Charts fall under? Descriptive, Inferential, or something else? As I'm thinking out loud...Control Charts use elements of Descriptive (central tendency, ...
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1answer
16 views

Can I still call the study placebo controlled if I give the control treatment to the test population as well

I am studying the efficacy of a novel drug in treating a cardiovascular disease with continuous variable results being measured and statistically analyzed. Suppose the control population is getting ...
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0answers
51 views

SAS/STAT: Testing the significance for Email Marketing Control groups with Proc Power

I'm trying to figure out a way to test to see if my control groups for email margeling campaigns will produce statistically significant re sluts. The group counts have already been set. The control ...
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1answer
824 views

R: Test for correlation with a covariate?

R: I have a linear correlation between two variables x and y, but need to control for a third variable that may be influencing the output. My question is about which test I should/ can use. Can I use ...
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1answer
54 views

Interpretation of linear regression where the outcome can only possibly cause the value of predictors and not viceversa

We want the verify the association between artificial pregnancy (artificial insemination) versus natural pregnancy and a series of pregnancy conditions (hypertensions, diabetes, etc). We first ...
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1answer
485 views

How find controls limits for CUSUM chart

I am trying to re-do a simulation work in quality control. In this simulation they use bisection search algorithm to find the control limits h (the threshold) that gives the desire average run length ...
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0answers
32 views

Interpretation of Model When Intentionally Excluding a Control Variable!

I am looking at factors affecting firm value (the dependent variable). I fitted the following model using OLS: $log(FirmValue_i)=\beta_0 + \beta_1Divers_i+ \beta_2HQLoc_i + \epsilon_i$ where ...
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96 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
21 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
42 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
108 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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50 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
27 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
16 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
140 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
58 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
560 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
1k 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
34 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
47 views

Control chart constants [closed]

When calculating Upper Control Limit (UCL) and Lower Control Limit (LCL) in control charts I use constants from ...
2
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1answer
289 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
62 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 ...
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1answer
373 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 ...
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1answer
29 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 ...