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Weekly GCP Challenge

Answer the questions below and then click the button. The next page will mark your answers and show you how well you have done compared with the previous people who have taken the tests.


Challenge: Power and Sample Size

Question Number 1:

If the sample size for a trial was calculated based on the following assumptions:

  • Response rate Group A = 65%
  • Response rate Group B = 50%
  • Significance level 5%
  • Power = 90%
  • Objective to show a difference between treatment groups


Which of the following changes to the assumptions would result in the required sample size increasing?

1) Changing the Expected Response Rate in Group A to 68% while all other assumptions remain the same

2) Changing the Expected Response Rate in Group B to 48% while all other assumptions remain the same

3) Changing the Power Level to 80% while all other assumptions remain the same

Which of the following is correct
A
 1 only
B
 2 only
C
 3 only
D
 None of them

Question Number 2:

If the sample size for a trial was calculated based on the following assumptions:

  • Mean Value Group A = 70
  • Mean Value Group B = 50
  • Standard Deviation = 10
  • Power = 90%
  • Objective to show a difference between treatment groups


Which of the following changes to the assumptions would result in the required sample size decreasing?

1) Changing the expected mean value for Group A to 80 while all other assumptions stay the same

2) Changing the expected mean value for Group B to 40 while all other assumptions stay the same

3) Changing the Power Level to 80% while all other assumptions remain the same

Which of the following is correct
A
 1 only
B
 1 and 2 only
C
 2 and 3 only
D
 All of them

Question Number 3:

A non-inferiority trial to compare the time to death for two oncology products has the non-inferiority criteria set out as

"Require to show that the hazard ratio of new treatment to old treatment is no more than 1.25" which in simple terms means to show that the new treatment is no more than 25% worse than the comparator.

Following discussions about the trial design it has been advised that you use a stricter criteria and have to show no more than 20% worse, ie a hazard ratio of 1.2

If all other assumptions remain the same, what effect will this change in non-inferiority criteria have on the required sample size?
A
 No change
B
 Increase Required Size
C
 Decrease Required Size
D
 Cannot tell

Question Number 4:

Your sample size calculations suggest you require 800 subjects to complete the trial. If the drop out rate is expected to be 20% how many subjects should you recruit?
A
 960
B
 1000
C
 1040
D
 1080

Question Number 5:

Your sample size calculations suggested you required 500 subjects to complete the trial. Half way through recruitment you perform a blinded review of the data to test the sample size assumptions. The review shows that the data for the primary endpoint is very much more variable than was assumed in the sample size calculations.

To overcome this incorrect assumption what could you do to the number of subjects required to be recruited?

 
A
 Reduce it
B
 Increase it
C
 Nothing
D
 Not enough information to tell

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