It will help you to understand the overall flow of information for your study.  Most people concentrate only on one small part, the statistical test, and forget the rest.

Starting with the physical phenomena that are being studied, we have to use some sort of measurement tool to quantify the aspects we want to study.  Then, some sort of data collection tool is used to capture the information.

Then, we create a master data set or sets from the data collection tools that will be frozen.  “Frozen” means that you will not ever edit those data again.  Ever.

If any data changes need to be made, they will be made in an analysis data set that is derived from the master data set.  Ideally, this will be done using some sort of automated system or programming steps, so that all changes from the master data set are documented.

If the analysis data set is created by hand, then you need to make notes of what changes were made.  I suggest including a text document with the analysis data set.  At some point, you are going to want to freeze the analysis data set so that you can follow the principle of analyzing only one data set.

Next, the data are manipulated using either a statistical package, a statistical language, or some other software  in order to produce statistical analyses, listings, tables, and figures.  Note that you may need to create further derived data sets in these tools in order to accomplish these tasks.

Again, if any manual steps are performed here, they need to be documented.

Finally, the statistical analyses, listings, tables, and figures are used to write the thesis or dissertation, to create presentations, or to write for publication.