Questions tagged [sas]

SAS is a statistical software package. Use this tag for any on-topic question that (a) involves SAS either as a critical part of the question or expected answer, & (b) is not just about how to use SAS.

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168 views

Strategies for model selection of non-nested GLMM models

What are the best strategies to select between a small collection of possible models when the models are non-nested and modeled using a GLMM with correlated residuals (longitudinal random effects or $...
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63 views

Parametric survival curve in middle of observation window

I am fitting a parametric survival model with a Weibull distribution that has pretty good results when checking the 12 month predictions versus the actual results. The issue I'm seeing is when looking ...
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130 views

How do I use the "correct" error term in PROC MIXED to conduct specific contrasts?

I have a SAS PROC MIXED question and I hope that y'all would be able to help me. It is my first time posting a question on here. First, an analog to help define the question: Imagine that a ...
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1answer
370 views

trough detection in time series

I have time series (daily readings), which can trend downwards. I would like to introduce a dichotomous dummy variable that indicates when the time series contains a trough (dummy=1) or not (dummy=0). ...
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1answer
43 views

Does it make sense to specify a repeated effect that does not appear in the model?

The concentration of a certain nutrient is measured in soil each fall after harvest in a set of research plots. I want to model the change in nutrient concentration over a number of years, but I'm ...
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1answer
980 views

How to use nearest neighbor to find similar population based on list of features

Nearest neighbor can classify new data point based on the k nearest neighbor's class. Assuming there is dataset A contains 10000 data points. There is also another dataset B contains 1 MM data points. ...
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83 views

"Uniform" Clustering

I have the data $\{(y_i,\omega_i), i=1,\dots,n\}$, where $y_i \in \mathbb{R}_+$ the response and $\omega_i>0$ a weight. Fixed $K>0$ I want to determinate $y_1^*,\dots,y_{K-1}^*$ such that $$ \...
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1answer
112 views

Probability models in SAS [closed]

What sort of tests are available in SAS that allow you to figure out what the probability of an event occurring is? And I do mean probability, not odds. Specifically, I would like to know what is the ...
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89 views

Logistic Regression Interaction vs conditioning on one level

I have a data set where the outcome is binary, and is fit as a function of two categorical variables (3-level location and 2-level status) and their interaction. I am interested in two things: ...
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1answer
261 views

Proc mixed in SAS with a random and repeated factor [closed]

I need to carry out a comparison test for the measures of absorbance between 2 types of tank: glass tank and plastic tank. The technician in the laboratory took randomly 5 plastic tanks and 5 glass ...
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1answer
407 views

PROC FACTOR SAS vs. prcomp() R

I wanted to know if anyone has ever come across research that was done comparing the output of a Principal Component Analysis (PCA) for PROC FACTOR in SAS versus the PCA output using the prcomp() ...
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123 views

PCA: Dimension Reduction

I ran PCA. Output is: . I am trying to increase the R-Square Value. In doing so, I want to only consider important variable. Till now I have cleaned the data by excluding the outliers and also by ...
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1answer
158 views

Count data model but also dealing with multiple comparison ? [closed]

I'm working on a project dealing with different treatments on the number of medical service in 1 year. I used negative binomial regression to estimate incident rate ratio after adjusting other ...
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1answer
1k views

SAS PROC LOGISTIC - why is Goodness of Fit test rejecting model?

I'm modelling a university applicants dataset using PROC LOGISTIC in SAS (9.2). The target variable is 'Enrolled y/n', and i'm modelling against a range of 13 variables (a mixture of indicator, ...
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497 views

Should we adjusted the weight according to sample size in propensity score with IPTW method?

I'm a new learner in biostatistics, recently doing a project that might need to use IPTW method for balancing covariates between treatment groups. When I read one of the sas references [Ref 1] for ...
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1answer
771 views

Significant autocorrelation in Bayesian regression model

By running the following Bayesian regression model using SAS 9.4: ...
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1answer
326 views

How to analyze binary categorical vs ordinal data?

Context: I have a dataset in which I am analyzing whether a patient having 1 disease (binary) influences the number of other diseases the patient has (ordinal; range = 0-7), which is the outcome ...
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165 views

Non-parametric test for trend

I have non-normal data which are sampled from roughly 4 subjects at 4 dose levels. Is there a nonparametric test for trend I can use in SAS?
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220 views

In SAS, does the using the GLM statement ABSORB invalidate the standard errors of the parameter estimates?

SAS provides a handy tool for handling panel models with a large number of groups by 'absorbing' those groups (PROC GLM; ABSORB). My understanding is that it factors the effect of the absorbed ...
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1answer
581 views

Propensity score matching with time dependent covariates in R or SAS

I'm trying to use propensity score matching (PSM) to find matched controls. The data is not cross-sectional and it has time dependent information (monthly, quarterly, etc.). Let us say I have ...
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1answer
522 views

How do I conduct an F-test for change in R^2 within SAS? [closed]

Suppose I have a simple model that looks something like this: y = {Block 1} x1 x2 x3 x4 {Block 2} x5 x6 x7 x8 If I want to conduct an F-test to see whether Block 2 produces a significant change in R^...
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1answer
491 views

SAS: Holt Winters Forecasting

If I have an estimate for Holt Winters model as the attached image. How do I interpret the estimates i.e the level, trend and seasonal smoothing weight.
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82 views

Simultaneous Marginal Homogeneity Score Statistic in R

I'm trying to implement in R the score test for Simultaneous Marginal Homogeneity with GEE as described in section 2.2 of Multivariate Extensions of McNemar’s Test - Klingenberg & Agresti [2006] ...
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673 views

Post Hoc for Fisher's Exact Test on a 5x5 table

I have two nominal variables which are site (location) and Depression Scores (PHQ-9). I have found a significant association after running a Fisher's Exact Test (with monte carlo approximation) on a ...
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1answer
3k views

Fishers exact test for more than 2x2 tables?

I have two categorical variables. One variable has 5 categories, the other has 7 (a 5x7 table) B/c there were less than 5 frequencies in each cell, instead of doing a chi square I want to do a fisher'...
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1answer
556 views

Random forest validation worse than one of its variables by itself

I am running a random forest in SAS using 6 variables, one of them being a score that works very well on its own. When I train the forest and validate on a test set, I'm seeing the following in terms ...
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1answer
794 views

APIM analyses of dyadic data: comparing HLM/MLM to SEM results, data structures, SAS Proc Mixed vs. Mplus and more!

I have run a set of dyadic analyses (distinguishable dyads: mom, infant) using both an SEM panel approach, as well as via an MLM/HLM approach using Mplus. In short, while there are subtle differences ...
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1answer
781 views

Fit a linear mixed model with only 1 group

In R, is it possible to force a lmer model with random effect to be fitted on data with only one level? We want to do this to keep the same model structure in rare case where our data only contains 1 ...
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101 views

Inflated Odds Ratios in a Mixed Effect Logistic Regression

I have a dataset with approximately 40,000 observations, which are dependent, coming from around 30,000 subjects. Most subjects has 1 observation, some have 2, a minority has 3, while 4 is rare. The ...
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1answer
1k views

ARIMA forecast has all values as zero

I'm trying to forecast 15 data points based on a time series of 61 data points. Each point is the daily total for a measure, and values of zero are possible. I do have the actual values for the 15 ...
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1answer
77 views

Odds of Ratio of 1 in logistic regression

I'm working with a dataset from Gapminder (www.gapminder.org), and I've been running some logistic regressions. As I understand it, if you get an Odds Ratio of exactly 1, then then interpretation is ...
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122 views

Simulating Data with MCMC with priors

I have data that are a sample of averages that each have a known variance/standard deviation. My goal is to have simulated data whose estimates vary in a similar way to the observed data. Through my ...
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356 views

Is SAS relevant software to modern machine learning? [closed]

I have an opportunity to attend SAS course and get certification, while getting my formal education. Is SAS relevant software for modern machine learning? I'm a former software engineer, so I'm ...
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1answer
19 views

2 Independent, 1 Dependent Analysis through SAS. Should I create a surface?

I have 12 runs of thermal data that each generate a matrix. I've added noise to my systematic data to simulate my detector. My output for each of these is a 500x500 matrix where the vertical axis is ...
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519 views

Variable selection - Logit model (using SAS)

I'm trying to find a model that will help predict the outcome of the dependent variable (binary). My test subset has 6,000 observations My variables are as follow: 6 categorical (with over 30 levels) ...
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1answer
725 views

When fitting Tweedie GLM in SAS, should I use the scale option?

In SAS proc genmod with dist=tweedie, when would you use scale=pearson or ...
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0answers
860 views

Mixed Anova in R

I am trying to do an anova anaysis in R. The experiment done had each subject tested in Method 1 and Method 2 as well a being in one of 4 different Levels (each subject in one group). The goal is to ...
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1answer
59 views

Reduce dimensionality of predictors for model building

I am trying to build a classification model. I have 600 variables to start with and was trying to reduce it a considerable set of variables to pass it to my model (like Logistic regression). Did ...
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1answer
413 views

Example of how Bayesian Statistics can estimate parameters that are very challenging to estimate through frequentist methods

Bayesian statisticians maintain that "Bayesian Statistics can estimate parameters that are very challenging to estimate through frequentist methods". Does the following quote taken from this SAS ...
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0answers
57 views

Fail normality test but the qqplot is a straight line [duplicate]

I am using SAS 9.4 . My aim is to find out whether my residual is normal or not, so i type this: ...
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1answer
1k views

R and SAS produce the same test-statistics but different p values for normality tests

I use Kolmogorov-Smirnov, Cramer-von Mises and Anderson-Darling tests to examine the normality of residuals of an OLS regression. It puzzles me that R and SAS, despite giving the same test-statistics ...
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2answers
6k views

Comparison among 3 paired data sets. (paired t-test, ANOVA?)

I measured 30 samples each with 3 devices. The devices are the same make and model, just different units. How do I statistically test if the devices measurements are the same or not? If I had two data ...
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102 views

ANOVA with Some Repeated Trials - Independence Assumption

I have some cross sectional data in which I would like to perform a basic ANOVA on. Some of the measurements are repeats from the same subjects, but the "independent variable" is not necessarily the ...
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118 views

How does one carry out the Wilcoxon-Gehan test for paired survival data?

In a 2-way crossover scenario, where subjects are randomized in a 1:1 ratio to either a AB or BA sequence, a time-to-response variable was measured after the dosing of treatment A or treatment B. ...
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1answer
550 views

In SAS Enterprise Miner, how can I tell the categories to which dummy variables correspond? [closed]

I'm new to SAS EM, and I'm having difficulty interpreting the results of a linear regression model. I have a categorical variable (state) that's been converted to binary dummy variables, but how can ...
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0answers
466 views

Interpretation of results of logistic regression (Analysis of effects vs Maximum Likelihood Estimates)

I have ran a logistic regression on my data in SAS. I get in the results a "Type 3 Analysis of Effects" which gives me a probability for my variables including a categorical variable. The probability ...
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1answer
6k views

Wilcoxon Rank Sum (Mann Whitney) test-SAS Results Interpretation

I need a clarification on interpreting Wilcoxon Rank Sum (Mann Whitney) test results using SAS. Here is a sample results look like. I am trying to form a hypothesis and interpret the results. In this ...
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1answer
183 views

Standard errors from quantile regression in SAS

Why the standard errors obtained from PROC GLM (for analysis of multiple regression) is larger compared to those from PROC QUANTREG (for analysis of quantile regression)?
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1answer
1k views

Newey West Covariance in SAS and in R are different

I am using the proc autoreg procedure in SAS and the sandwich library in R to calculate Newey West covariance for a linear model....
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1answer
91 views

2 non-linearly correlated variables

I am currently looking at some code that uses 2 independent variables, which look as follows when scatter plotted: Clearly, they are (non) linearly correlated. IMHO this violates a key assumption of ...

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