The factors that have the largest impact on data precision or accuracy are the:

a$.$ data collection method and sample characteristics

b$.$ research design and incidence rate

c$.$ research budget and time frame

d$.$ questionnaire length and structure

All of the following tactics can be used to improve mail survey research, except:

a$.$ providing respondents with the emailer's email address and phone number

b$.$ offering incentives for participation

c$.$ sending a second copy of the questionnaire to non$-$respondents

d$.$ sending a prenotification postcard or letter prior to the survey