Measuring the concept of the public’s approval of the president

A problem of measurement bias, invalidity, unreliable, or none of the above.  Measuring the concept of the public’s approval of the president by using a series of survey results asking respondents whether they approve or disapprove of the president’s job performance.

(b) Measuring the concept of political corruption as the percentage of politicians in a country in a year who are convicted of corrupt practices.
(c) Measuring the concept of democracy in each nation of the world by reading
their constitution and seeing if it claims that the nation is
” democratic.”