# Dependent Variable

The dependent, or response, variable is the variable being tested in the model. You can either provide your dependent variable values in the input data set or you can have Joinpoint calculate them from other variables in the input data set (e.g. a crude rate can be calculated from variables with the count and the population).

## Types of Dependent Variables Accepted by Joinpoint:

The following dependent variable types can be analyzed by Joinpoint:

## Standard Error Calculations:

When Joinpoint computes the Dependent Variable, the following formulas will be used to compute the associated standard errors.

## Standard Error for Crude Rate

This calculation assumes that the counts have Poisson distributions.

$SE_{crude} = \frac{\sqrt{count}}{population} \times\ 100,000$

## Standard Error for an Age-Adjusted Rate

This calculation assumes that the counts have Poisson distributions.  Suppose that the age-adjusted rate is for an age group comprised of ages x through y.

$SE_{AArate} = \sqrt{\sum_{i=x}^{y} \left( \frac{stdpop_i}{\sum {}_{j=x}^{y} stdpop_j} \right)^2 \times\ \left( \frac{count_i}{population_i^2} \right)} \times\ 100,000$

## Standard Error for Proportions and Percentages

For consistency, assume that percents are transformed to proportions before analysis.

$SE_{proportion} = \sqrt{\frac{p_i \left( 1 - p_i \right)}{n_i}}$

Where pi is the proportion and ni is the sample size of the ith observation.

$SE_{percentage} = \sqrt{\frac{p_i \left( 1 - p_i \right)}{n_i}} \times\ 100$

## Edits performed on the Dependent Variable:

• When a session is executed, Joinpoint will first edit the input data file.  For a list and description of all data errors and warnings produced by Joinpoint, please see the "Job Execution - Errors and Warnings" help section.

## Variables:

One or more of the following variables will need to be specified in the input data file depending on the Calculated/Provided, Type, and Heteroscedastic Errors Options selections:

• Count Variable
• Population Variable
• Standard Error - this variable can be found in within the Heteroscedastic/Correlated Errors Option box and is shown only for the applicable Heteroscedastic option.
• Standard Population
• Numerator Variable – this variable replaces the “Count” variable when appropriate
• Denominator Variable – this variable replaces the “Population” variable when appropriate

Joinpoint does allow any variable value to be provided in fractional form (e.g. 410.375).

Calculate Type Heteroscedastic Errors Required Variables Required Variables Required Variables Required Variables
No Count Constant Variance Count
No Count Standard Error Count Standard Error
No Count Poisson Variance Count
No Crude Rates Constant Variance Rate
No Crude Rates Standard Error Rate Standard Error
Crude Rates Poisson Variance n/a
No Age-Adjusted Rates Constant Variance Rate
No Age-Adjusted Rates Standard Error Rate Standard Error
No Age-Adjusted Rates Poisson Variance n/a
No Proportion Constant Variance Proportion
No Proportion Standard Error Proportion Standard Error
No Proportion Poisson Variance n/a
No Percent Constant Variance Percent
No Percent Standard Error Percent Standard Error
No Percent Poisson Variance n/a
No Other Constant Variance Other
No Other Standard Error Other Standard Error
No Other Poisson Variance n/a
Yes Count Constant Variance n/a
Yes Count Standard Error n/a
Yes Count Poisson Variance n/a
Yes Crude Rates Constant Variance Count Population
Yes Crude Rates Standard Error Count Population
Yes Crude Rates Poisson Variance Count Population
Yes Age-Adjusted Rates Constant Variance Count Population Age Group Standard Pop
Yes Age-Adjusted Rates Standard Error Count Population Age Group Standard Pop
Yes Age-Adjusted Rates Poisson Variance n/a
Yes Proportion Constant Variance Count Population
Yes Proportion Standard Error Count Population
Yes Proportion Poisson Variance n/a
Yes Percent Constant Variance Count Population
Yes Percent Standard Error Count Population
Yes Percent Poisson Variance n/a
Yes Other Constant Variance n/a
Yes Other Standard Error n/a
Yes Other Poisson Variance n/a
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