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Posted On: 10/20/2020 8:24:29 AM
Post# of 148902
To my knowledge e.g. the dexamethasone study used a two-tailed to.
For one-sided p-value you can roughly divide the value by two.
"As stated in the protocol, appropriate sample sizes could not be estimated when the trial was
being planned at the start of the COVID-19 pandemic. As the trial progressed, the trial Steering
Committee, blinded to the results of the study treatment comparisons, formed the view that, if
28-day mortality was 20% then a comparison of at least 2000 patients allocated to active drug
and 4000 to usual care alone would yield at least 90% power at TWO-SIDED P=0.01 to detect a
clinically relevant absolute difference of 4 percentage points between the two groups (a
proportional reduction of one-fifth). Consequently, on 8 June 2020, the Steering Committee
closed recruitment to the dexamethasone arm since enrolment exceeded 2000 patients."
For one-sided p-value you can roughly divide the value by two.
"As stated in the protocol, appropriate sample sizes could not be estimated when the trial was
being planned at the start of the COVID-19 pandemic. As the trial progressed, the trial Steering
Committee, blinded to the results of the study treatment comparisons, formed the view that, if
28-day mortality was 20% then a comparison of at least 2000 patients allocated to active drug
and 4000 to usual care alone would yield at least 90% power at TWO-SIDED P=0.01 to detect a
clinically relevant absolute difference of 4 percentage points between the two groups (a
proportional reduction of one-fifth). Consequently, on 8 June 2020, the Steering Committee
closed recruitment to the dexamethasone arm since enrolment exceeded 2000 patients."
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