In GCP trials, what level of significance is commonly used for hypothesis testing?

In GCP trials, what level of significance is commonly used for hypothesis testing?

• A. Two-sided 0.05
• B. One-sided 0.05
• C. Two-sided 0.01
• D. One-sided 0.10

Answer: (A)

The level of significance commonly used in GCP trials is a two-sided alpha of 0.05. This means you’re testing for an effect in either direction and you're willing to accept a 5% chance of a false-positive conclusion about a treatment effect. A two-sided test splits that 5% into 2.5% in each tail, aligning with 95% confidence intervals and regulatory expectations that an effect could go either way. One-sided 0.05 would only guard for an effect in one direction, which can miss important safety or harm signals and is generally not preferred in GCP unless there is a strong, justified reason. A lower alpha (0.01) is more stringent and requires larger sample sizes to achieve the same power, while a higher alpha (0.10) increases the risk of false positives.

The level of significance commonly used in GCP trials is a two-sided alpha of 0.05. This means you’re testing for an effect in either direction and you're willing to accept a 5% chance of a false-positive conclusion about a treatment effect. A two-sided test splits that 5% into 2.5% in each tail, aligning with 95% confidence intervals and regulatory expectations that an effect could go either way. One-sided 0.05 would only guard for an effect in one direction, which can miss important safety or harm signals and is generally not preferred in GCP unless there is a strong, justified reason. A lower alpha (0.01) is more stringent and requires larger sample sizes to achieve the same power, while a higher alpha (0.10) increases the risk of false positives.