Evidence based medicine 1 (ignore)

Question 1

What are the 2 ways of describing probability ?

Answer 1

• P Values - A numerical value indicating the probability that this observation has occurred due to chance
• Confidence intervals - A way of indicating a range of values which probably contain the “true” value

Question 2

Describe confidence intervals

Answer 2

“There is a 95% chance that the true result for this population lies between …. and ….”

Or

“If this experiment was repeated, 95% of the time the results would fall between … and …”

Question 3

What is the null hypothesis ?

Answer 3

The hypothesis that there is no significant difference between specified populations, any observed difference being due to sampling or experimental error.

Question 4

What is Type 1 error?

Answer 4

Rejecting the null hypothesis when it is true e.g. false positive

Question 5

What is type 2 error ?

Answer 5

Accepting the null hypothesis when it is false e.g. False negative

Question 6

Describe the difference between clinically significant and statistically significant

Answer 6

• Results are said to be “statistically significant” if the probability that the result is compatible with the null hypothesis is very small.
• Clinical significance, or clinical importance: Is the difference between new and old therapy found in the study large enough for you to alter your practice?