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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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17 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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7 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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18 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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21 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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18 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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16 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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21 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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23 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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21 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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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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13 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
25 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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16 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
25 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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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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21 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
15 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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33 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
251 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
53 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
236 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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31 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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57 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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19 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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30 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
71 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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42 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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25 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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14 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
126 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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52 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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455 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
535 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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33 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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31 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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40 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
186 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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56 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
248 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
26 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 ...
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1answer
17 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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70 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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1answer
244 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
52 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 ...
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1answer
443 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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21 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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2answers
61 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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2answers
7k 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 ...