Poisson regression is for modeling count variables. Please note: The purpose of this page is to show how to use various data analysis commands.  It does not cover all aspects…
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Introduction Power analysis is the name given to the process for determining the sample size for a research study. The technical definition of power is that it is the probability…
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Probit regression, also called a probit model, is used to model dichotomous or binary outcome variables. In the probit model, the inverse standard normal distribution of the probability is modeled…
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Introduction Power analysis is the name given to the process for determining the sample size for a research study. The technical definition of power is that it is the probability…
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Robust regression is an alternative to least squares regression when  data is contaminated with outliers or influential observations and it can also be used for the purpose of detecting influential…
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Examples Example 1. A company that manufactures light bulbs claims that a particular type of light bulb will last 850 hours on average with standard deviation of 50. A consumer…
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Examples Example 1. A clinical dietician wants to compare two different diets, A and B, for diabetic patients. She hypothesizes that diet A (Group 1) will be better than diet…
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Examples Example 1. A company markets an eight week long weight loss program and claims that at the end of the program on average a participant will have lost 5…
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Note: This page uses SAS 9.2. The tobit model, also called a censored regression model, is designed to estimate linear relationships between variables when there is either left- or right-censoring…
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Zero-inflated negative binomial regression is for modeling count variables with excessive zeros and it is usually for over-dispersed count outcome variables. Furthermore, theory suggests that the excess zeros are generated…
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