Week 15 Flashcards
When is the P value used?
when we want to see how likely that the hypothesis is true.
Why would a hypothesis be used?
When comparing the measurements of two or more groups:
We may make a Hypothesis on the difference between them.
And the P value is used t see how likely the hypothesis is true
The significance level describes what?
describes the likelihood that the null hypothesis is correct.
What does significance mean?
commonly used method for determining difference between 2(or more) sets of data (e.g. before and after treatment) is hypothesis testing.
This method for statistical inference dates back to the 20s
This method is widely misused and often misinterpreted
How do you find significance in results?
begin with we generate a null hypothesis (often given the symbol H0)
This is the hypothesis that there IS NO DIFERENCE METWEEN TWO SAMPLES/POPULATIONS
In the example above H0 == no significant deference between e.g. mean cure-rate before and after treatment.
What do P-Values actually mean?
P = 0.5 means that that the probability of the difference having happened is 0.5 in 1
In other words the probability of observing the outcome you did was 50%
It’s often stated that the smaller the P-value the less likely it is that the difference happened by chance and so the higher the significance of the finding
How can P-Value be misused?
P-values (and by association statistical significance) is sometimes automatically associated with relevance.
A small sample will usually return a non-significant p-value (P≥ 0.05) even if there actually is a difference.
A large sample size will very often return a significant p-value (P < 0.05) even if the difference in question is really very small and of no likely relevance.
