World Health Organization
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 Pharmaceutical Policy

    Improving Access to and Use of Essential Medicines



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IN THE SPOTLIGHT

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Medicines and Insurance Coverage (MedIC) Initiative

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Glossary of Terms Used for Pharmaceuticals and Pharmaceutical Policies in Low- and Middle-Income Countries
 

 

















Analytical Methods for Longitudinal Analysis – Tools and Analysis

Controlled interrupted time series designs, the strongest quasi-experimental designs, are crucial for policy evaluation around the world. However, appropriate software to properly conduct segmented regression analyses of interrupted time series studies remains too expensive and difficult to use for many researchers. In particular, it is necessary to control for correlation between subsequent observations for arriving at proper inferences from these study designs.

We have developed an Excel and R-based tool for performing segmented regression analyses of interrupted time series studies. The R statistical package is freely-available on the Internet. While R can run appropriate models, it is difficult to learn. We therefore have developed an Excel interface to the R-program. The resulting analysis tool will use the familiar Excel spreadsheet data entry and a graphical user interface to set statistical model parameters and obtain results from the R-program that will perform in the background.

A preliminary presentation that described development and use of the tool can be found here. The program and draft User’s Guide will be available soon.

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Information from the Third International Conference for Improving Use of Medicines, ICIUM2011