Final answer:
Invalid study results are often due to issues with measurement irregularities, sample size, experimental design and ethics, inability to test specific variables, and misinterpretation of results, including false negatives.
Step-by-step explanation:
Condition Causing Invalid Study Results
Conditions that can produce invalid results in a study include irregularities in the object being measured, such as a poorly designed survey or inadequate polling methods leading to erroneous predictions in public opinion research. Furthermore, if a study's sample size is too small, it may yield unreliable results. For instance, while crash testing cars or conducting medical tests for rare conditions, the sample size might be inherently small, yet it's important to aim for larger samples when possible for greater reliability. Another critical aspect of reliable research is the experimental design and ethics involved. Every study must consider random assignment of subjects to treatment groups and include a control group, using placebo treatments and blinding to maintain the integrity of the study. Other factors may include bias in interpretation, as illustrated by an author drawing incorrect conclusions from test evidence, without considering alternative perspectives or contributing variables.
Occasionally, testing certain variables is either impossible, impractical, or unethical. Researchers might rely on observational studies or indirect evidence, as seen historically in experiments for conditions like scurvy or in modern research on the nutrition of astronauts. Lastly, studies may encounter false-negative results impacting the outcome, such as a test indicating no infection when one exists. All these factors must be addressed to ensure a study's results are valid.