Answer: this corresponds to a chi-square test for Goodness of Fit.
Step-by-step explanation:
Goodness of fit Chi-squared test gives confirmation on whether a separately observed frequency distribution differs from a theoretical or general distribution.
In this case, the researcher studies a fraction of income earners - low income earners. He is interested in knowing whether the distribution of pay of low income earners is different from the distribution of pay of ALL income earners.
This survey hence corresponds to a chi-square test for goodness of fit.