A Researcher Tests the Effect of a New Laparoscopic Treatment

A researcher tests the effect of a new laparoscopic treatment for chronic shoulder dislocation, comparing it with an older treatment. The results are statistically significant, and the researcher states in the study findings that there is evidence that the treatment has promise for widespread application. A subsequent replication study fails to show statistical significance. A third and fourth study produce the same effects as the second. Sample sizes are determined to be sufficient in all four studies. What is the most likely explanation here?

A) A Type I error occurred in the first study.
B) A Type II error occurred in the second, third, and fourth studies.
C) External validity is excellent.
D) Operationalization of variables was faulty.

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