eCRF creation rules

  1. The record ID must be the first variable of the first form.
    Never use special symbols or letters (e.g., accented letters) for the ID.
  2. Group similar variables together.
  3. Keep forms short.
    Shorter the forms are, it is easier to fill out and offer more options for storing data. Data entered are not saved until the data submitter clicks ‘save’ or survey participants click ‘go to next page’ or ‘submit’.
  4. Minimise the use of free response fields.
    Whenever possible, use multiple choice instead of asking the data submitter to list information to minimize inconsistent responses and typos. If you use a free response field, verify the data type whenever possible. This will help minimize the number of typos. Unvalidated fields are saved as text and imported into statistical analysis programs as text. If you want to analyse the information as a number, your statistician will have to manually change the field types. If it’s applicable, set maximums and minimums for numeric fields to minimize data entry errors. REDCap will let you continue if you enter numbers outside this range, but it will warn you that the number is out of range. This will help minimize errors while allowing outliers to be accounted for.
  5. Field Notes.
    Use field notes to help data submitters enter information correctly. For example: units the measurement should be entered.
  6. Minimize switching between fields where you type (text fields, drop-down menus) and fields where the mouse is used (such as radio buttons and check boxes).
  7. Split variables into the key components you want to analyse.
    For example, if you are collecting addresses and want to analyze at both the region and city level, make those separate fields.
  8. Be consistent in the coding of the variables.
    Avoid yes/no and true/false fields, which usually cause problems if you need to add a third option later – stick to radio buttons and drop-down lists. Don’t recode variables once you’ve started collecting data—this will corrupt your data. Just add the next number. The numbers do not have to be in order in the list. Code “unknowns” as a high number that stands out, like 999. If you have multiple questions that will use the same answer choices, code them all the same.
  9. Variable names.
    Variable names should be short, alphanumeric, easy to type, and ideally have some level of meaning—these are the labels that REDCap will use to locate your data, and these are what you will be typing over and over when you are doing your analysis. Variable name should not be changed once data collection has begun. If you change a variable name, you will also to change all piping, calculations, and branching logic associated with it.
  10. Calculated fields
    REDCap is capable of doing calculations, but it is not designed as a statistical tool—save complex calculations for back end analysis. As a rule of thumb, use calculations in REDCap if you need to see that calculation for the data collection process—otherwise, save calculations for back end analysis. You can export your data from REDCap to CSV, SPSS, SAS, R, and Stata.
  11. Branching logic
    Branching logic is a great way to hide fields that will be irrelevant to certain users and streamline and customize the data entry process. Branching logic goes in the child field—the field that you want to hide. You can either use the drag and drop menu or write out advanced branching logic.
  12. Data dictionary
    A data dictionary is an alternate way to build your project (as opposed to the online design). You can create or view the data dictionary as a csv file in Excel. The data dictionary is particularly useful when you have to do repetitive work that requires few or small changes. For example: If you need to apply the exact same branching logic to many fields, you can do it in the data dictionary much more quickly with copy and paste. Another example: If you need to have many places to list medications being taken (name, dosage, date), it is much faster to make one set of fields in the Online Designer and then copy and paste the remaining fields from that in the data dictionary. You can use find-replace to change the 1 or 2 characters per row that will need to be changed.
  13. Survey links
    Use the “long” public survey URL instead, as some users may have trouble redirecting from a shortened URL.
  14. Above all, think about how you will enter the data and how you want to analysis it while you’re building your database. If possible, speak with your data enterers and your statistician before you build your database and incorporate their suggestions in your database design.