The formula for calculating the required sample size is: [ n = \frac{{Z^2 \cdot p \cdot (1 - p)}}{{E^2}} ] Where: (n) represents the required sample size. (Z) is the z-score corresponding to the desired confidence level (for a 95% confidence level, (Z \approx 1.96)). (p) is the proportion of respondents who believe human activity plays a part in global warming (expressed as a decimal, so (p = 0.72)). (E) is the margin of error (expressed as a decimal, so (E = 0.04)). Plugging in the values: [ n = \frac{{(1.96)^2 \cdot 0.72 \cdot (1 - 0.72)}}{{0.04^2}} ] Solving for (n): [ n \approx 1,507 ] Therefore, the follow-up survey should aim for a sample size of approximately 1,507 respondents to achieve a 95% confidence level with a margin of error of 4%. Keep in mind that other factors, such as the survey methodology and population characteristics, may also influence the sample size calculation