1. Dealing with nonresponse
Compare respondents to the population.
This requires that the researchers have information about the background characteristics of the population, for example, size of the grant or type of institution that received a grant.
If there are differences, the results only can be generalized to the respondents. We to see the NO DIFFERENCE TO BE ABLE TO GENELIAZE TO THE POPULATION
This approach is not very sensitive if there is a high response rate because of the large overlap between the respondents and the population.

2. If NO DIFFERENCE, GENERALIZATION TO THE SAMPLE THEN TO POPULATION
Compare respondents to non-respondents.
This method also requires the researchers have background information about both groups. This could be the size of the grant or, perhaps, whether the grant was made to a two-year or four-year institution. Follow-up on a random sample (10% - 20%) of non-respondents. Usually telephone or personal interviews are used. Questions from the survey are used to guide the interviews. DOUBLE-DIPPING
If NO DIFFERENCE, GENERALIZATION TO THE SAMPLE THEN TO POPULATION

3. Compare early to late responders.
Some research has shown that late responders are similar to non-respondents so late responders can be used as a proxy for non-respondents.
Actual survey responses are compared to determine if there are differences between the two groups
NO DIFFERENCE GENERELIAZE TO THE POPULATION