A national research group now recruits survey participants through a smartphone app and by sending SMS invitations instead of using landline calls. Explain how these recruitment methods can introduce nonsampling error, and identify the main types of nonsampling error likely to arise.

Only sampling variability increases because apps and SMS make the sample size smaller, so only random error is affected.

Coverage error, nonresponse error, measurement error, and processing error are likely; smartphone-only recruitment excludes non-smartphone users and SMS response rates are selective.

These methods only introduce measurement error because the wording on a smartphone is always misunderstood, so coverage and nonresponse are unaffected.

The only issue is processing error due to app crashes, so coverage, nonresponse, and measurement errors are not relevant.