Final answer:
The population parameter of interest is the proportion of the US population favoring vaccination proof for air travel, and the point estimate of this parameter from the Gallup poll is 57%.
Step-by-step explanation:
The population parameter of interest in the Gallup poll is the proportion of the entire U.S. population that would favor requiring proof of COVID-19 vaccination for air travel. As the survey was conducted among 3,731 randomly sampled US residents, the value of the point estimate for this parameter is the percentage of respondents who favored the requirement, which is 57%. A random sample is meant to be representative of a larger population, and the point estimate is the survey's best guess at what that population parameter might be. However, the accuracy of this estimate is subject to the sample size and how well it represents the population, in addition to the level of confidence and margin of error associated with the statistical methods used.