The weaknesses that exist in the selected primary data collection methods is that the interview method is applicable only where the respondent can be contacted for face to face questions and interviews. As a result those respondents who are unable to schedule meetings for the interview cannot be targeted. Aside from this as the interview based method normally has only one respondent per interview, the number of respondents that can be targeted using the method is limited as increasing the number of respondents can increase the expense of the research.
The weakness of the questionnaire based survey is that while it does target multiple respondents, the integrity of the answers provided by the respondents cannot be ensured. For this as a result the triangulation questions can be employed to cross check and verify the answers provided by the respondents.