Also, ratings of performance on a questionnaire can be highly subjective, and one person's rating of 'excellent' may be another person's 'acceptable.' How can Sam maximize the response rate to the survey?

Personalizing the submitting responses is essential -- sending follow-up emails to individuals who do not respond is a good idea as is electronically 'thanking' those who do submit a response. The latter practice will ensure that responders will continue to respond to such surveys in the future. Also, if at all possible, having a small prize for a randomly...

What amendments to these questions do you think Sam made after the pilot testing?
The extract measured the gap between expected service and actual service. Describing exactly what types of 'services' to which the respondent is referring is essential, as is measuring what constitutes 'good' or excellent service in the eyes of respondents.