This is perfectly normal, so researchers have developed acceptable methods for handling missing data.
In absolutely no instances should a researcher make up data.
Instead, the researcher should educate themselves about acceptable practices for overcoming the problem of missing data. First, a participant might have just skipped one item on a questionnaire.
Strategies for overcoming missing data on just one or two items will be described when discussing data analysis in Coding Data from the Instrument.
These sample sizes should be accurately reported in a column in the table of mean scores in the results section.
In other cases, missing data may exclude the participant from the study entirely.
Since the target population and sampling technique have already been identified, this step simply consists of writing the relevant sections for the research report.
Recall that the researcher has an important responsibility to systematically report on the methods of a research study so other researchers can replicate the work.
According to APA guidelines, the major demographic characteristics of the sample must be described, including sex, age, and race/ethnicity as well as socioeconomic status and disability status where possible and appropriate.
This means that the researcher must tell how many participants were male/female, the average age of the sample, and describe the ethnicity of participants.