Two scientific studies estimated the proportion of a certain bacterium in water samples. Study 1 and Study 2 used the same testing method. Their results:
| Study | Proportion | Margin of Error |
|---|---|---|
| 1 | 55% | 6% |
| 2 | 45% | 4% |
What is the most credible reason that Study 1's margin of error exceeds Study 2's margin of error?
Study 1 reported a higher proportion.
Study 1 measured samples at more locations.
Study 1 had a smaller sampling error.
Study 1 had a smaller sample size.
