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Your LimeSurvey version: 4.2.5
Own server or LimeSurvey hosting: Own server
Theme: Bay of many
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I am using multiple short text Type: Q question. For sub questions I am asking my respondents to fill their telephone number SQ01 and email SQ03. I am also asking them to repeat their telephone number SQ02 and email SQ04. I would like to know if it's possible for SQ02 to validate SQ01 (same with the SQ04 and SQ03) and if the response doesn't match the respondent to get an error, and what would the code for this look like. I think it might be easier to do this with few short free text: Type: S but I'd prefer to use multiple short text because of it's display type. 

Thanks in advance 

Hi,
consider, what has to be fulfilled.
This you enter in "question validation equation".

Both (Q1_SQ01 and Q1_SQ02) must not be empty " !is_empty(...) "and 
Q1_SQ01 must be equal Q1_SQ02. " Q1_SQ01==Q2_SQ02 "

Joffm

Thank you