Clinical trials- sample size and power

Question 1

Power

Answer 1

The probability of being able to detect a treatment difference if one truly exists

**80% is min acceptable value

Question 2

When do you need to use power?

Answer 2

Use when reading a clinical trial that has insignificant results, and then need to determine if the trial has the power to detect a clinical difference

Question 3

What do you want to accept for Type 1 error rate?

Answer 3

Usually 0.05
But if a trial is very expensive or potentially harmful, you might want to set the level at 0.01 or even lower

Question 4

How small a clinical difference do you want to detect?

Answer 4

-will need to decide how big a difference is clinically or economically important for your primary outcome measure
**more animals are needed to detect small differences

Question 5

Beta or power level

Answer 5

Power=1-beta

Usually set to 80% (beta= 0.2)

Question 6

5 elements of power

Answer 6

1. Type 1 error (false claim risk)
2. Type 2 error (missed opportunity risk)
3. What type of results is expected in the control group?
4. How small a difference is important to detect?
5. The number of individuals in each treatment group

Question 7

Steps of Evidence based medicine

Answer 7

1.Ask
2. Acquire
3. Appraise
4. Apply
5. Assess

Question 8

Apply

Answer 8

-Have the answers to your PICO that can be applied to your circumstances and your patients
-use evidence you have read to help with decision making
-look at how relevant evidence is= external validity!

Question 9

Four questions that may arise when applying the evidence

Answer 9

1. What are the potential effects of treatment, both beneficial and harmful?
2. Are there difference in the effects of treatments on different sub-groups of animals
3. Are there differences in levels of risk between different groups/sub-groups of animals
4. How do the benefits and harms relate to the individual animal or group of animals you have in front of you?

Question 10

Promote/discuss important evidence

Answer 10

-Need to share important evidence with colleagues
-Promote new evidence to clients to ensure owner compliance
-Design a strategy for change in your practice

Question 11

Assess

Answer 11

-Final step of EBVM
- Ask whether the changes in strategy you made has made a difference, improvement, decline?