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Joinpoint: Frequently Asked Questions

Program Changes

  1. What are the most recent changes to the Joinpoint program?
  2. How can I replicate previous results with a newer version of Joinpoint?

Model Estimation and Selection Methods

  1. Why doesn't the Joinpoint program give me the best possible fit? I can see other models with more joinpoints that would fit better. Exactly how does the program decide which tests to perform and which joinpoint model is the final model?
  2. Describe the permutation test used here.
    1. How many permuted data sets should I use?
    2. What does the p-value mean for joinpoint?
    3. Why are new significance levels being used in Version 3.0 and succeeding releases?
  3. What is the Bayesian Information Criterion method for selecting the best model?
  4. Why should I use the Permutation Test (PT) when Bayesian Information Criterion (BIC) is so much faster?
  5. Should I use the linear or log-linear model?
  6. When running the test for pairwise differences with the Coincident option, should I use a weighted or unweighted model?
  7. Does the test of parallelism of two series require the series to be uncorrelated?
  8. Can the Joinpoint software estimate the autocorrelation parameter?

Applications of Joinpoint

  1. I used the program on SEER data and do not get the same answers as in the SEER Cancer Statistics Review. Why?
  2. How do I import Joinpoint's graphs into a graphics software package such as Excel, Harvard Graphics, or PowerPoint?
  3. When I fit a Joinpoint model to find the rate trend, why doesn't the APC for one of the segments match the APC found by SEER*Stat for the corresponding segment?
  4. Sometimes, the change in the slopes between two segments is not statistically significant (p-value>0.05) from the t-test, but there is a joinpoint between the two segments or vice versa. Why?
  5. Sometimes, the APC for one segment is significantly different from zero, when an extra joinpoint in the segment is determined by the Joinpoint software, neither APCs for the two consecutive segments are significant. Why?
  6. Can I do Joinpoint regressions where the time intervals are not equally spaced or the time points are not integer?
  7. Can Joinpoint be used to model proportions or percents?
  8. How does the Joinpoint software deal with zeros in the dependent variable?
  9. Can I use Joinpoint to project or extrapolate into the future?