18 Questions
What is a common issue that can lead to an underpowered trial in a clinical trial?
Participants missing outcome data
What is the intention-to-treat principle in clinical trials?
Analyzing participants based on the treatment they were randomized to
Why should sample size be specified in the grant application and protocol?
To ensure that the trial is adequately powered
What is the recommended pilot trial sample size per treatment arm for a medium standardised effect size?
15
What is the purpose of inflating the sample size in a clinical trial?
To account for participant dropout
What is the primary purpose of a pilot trial in clinical trial design?
To demonstrate the feasibility of a larger trial
What is the relationship between the sample size needed at recruitment and the retention rate at the primary follow-up timepoint?
Sample size needed at recruitment = 1 / Retention rate at primary follow-up timepoint
Why is formal hypothesis testing for effectiveness not recommended in a pilot trial?
Because the pilot trial is usually underpowered to do this
Why is sample size calculation considered an educated guess?
Because it depends on various factors, including the type of outcome variable and the expected effect size
What is the recommended sample size for estimating a participation rate of 50% to within a 95% confidence interval of +/-10%?
100
What is the purpose of estimating a sample size for a pilot trial?
To determine the feasibility of a larger trial
Why should the size of a pilot trial be large enough?
To convince a funder to support a larger trial
What is the primary objective of performing sample size calculations in a clinical trial?
To avoid making an error in the study
What is the purpose of power calculations in a clinical trial?
To estimate the number of participants required to achieve a statistically significant result
What is the main reason for conducting sample size calculations in a clinical trial?
To ensure the trial is ethical and justifiable
What is the role of the sample size calculation in a clinical trial?
To estimate the number of participants required to achieve a statistically significant result
What is the consequence of underestimating the sample size in a clinical trial?
The study may be underpowered, leading to an increased risk of type II error
What is the relationship between the sample size and the power of a clinical trial?
As the sample size increases, the power of the study increases
Learn about the practical considerations in calculating sample sizes for cluster randomized controlled trials (cRCTs), including budget constraints and accounting for participant dropout. Understand how to handle missing outcome data in clinical trials.
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