Final answer:
High external validity implies that the research findings can be generalized to real-world settings, but may indicate a potential trade-off with low internal validity, which is the ability to demonstrate a cause-and-effect relationship within the experimental design.
Step-by-step explanation:
High external validity in field experiments is generally considered to be beneficial because it enhances the generalizability of the study's findings to real-world settings. However, high external validity may sometimes come at the expense of internal validity, which refers to the degree to which an experimental design allows for the conclusion that the independent variable caused the observed effects. This potential negative aspect of high external validity implies that if the experiment has high external validity, it may show a trade-off by having low internal validity (Option 1). This means that due to less control over variables in field experiments, it can be more challenging to establish a clear cause-and-effect relationship.
It is important to note that high external validity does not necessarily mean that the other options are negative outcomes by default. Low reliability (Option 2), low generalizability (Option 3), and low statistical power (Option 4) are distinct concepts and are not intrinsic consequences of high external validity. Researchers must balance the strengths and limitations of their experimental design to achieve the desired levels of reliability, generalizability, and statistical power, while also considering ethical constraints and the experimental control required for a valid and accurate study.