POPH192 - Lecture 24 Flashcards
what can p values do?
help decide if the study is due to chance or not
- the probability that the study result is wrong and is due to chance/sampling error
definition of p values?
probability of getting a study estimate (or one further from the null), when there really is no association, just because of sampling error
relationship between p value and chance?
the higher the p value, the more likely the association is due to chance
what does a small p value (<0.05) mean?
small chance the association found is incorrect (due to chance) and there is no true association
what does a large p value (>0.05) mean?
a larger chance the association found is incorrect (due to chance) and there is actually no association
what is the p value if the 95% CI includes the null value?
p >0.05
what is the p value if the 95% CI doesn’t include the null value?
p < 0.05
what significance is it when p > 0.05?
not statistically significant
what significance is it when p<0.05
statistically significant
what are the 2 types of hypothesis of p values?
- null hypothesis (Ho)
- alternative hypothesis (Ha)
what is the null hypothesis?
- there is no association between exposure and outcome
what is the alternative hypothesis?
- truly is an association between exposure and outcome?
what happens to hypothesis when p > 0.05?
- fail to reject null hypothesis
- reject alternative hypothesis
- not statistically significant
what happens to hypothesis when p < 0.05?
- reject null hypothesis
- accept alternative hypothesis
- statistically significant
useful flow chart :)))
what is the interpretation of the study when the p value is given and is less than 0.05?
- since the p-value is less than 0.05 the association is statistically significant
- we reject the null hypothesis and accept the alternative hypothesis
- chance is unlikely an explanation of study finding
what is the interpretation of study when you assume the p value from the 95% confidence interval and it is less than 0.05?
- this is a statistically significant association at the 0.05 level as the 95% confidence interval doesn’t include the null value of 1
- we reject the null hypothesis and accept the alternative hypothesis
- chance is an unlikely explanation of study finding
what is the interpretation of the study when the p value is given and it is greater than 0.05?
since the p-value is greater than 0.05, the association is not statistically significant
- we fail to reject the null hypothesis and reject the alternative hypothesis
- chance is a likely explanation of study findings
what is the interpretation of the study when you assume p value from the 95% CI, and it is greater than 0.05?
this is not a statistically significant association at the 0.05 level as the 95% confidence interval does include the null value of 1
- we fail to reject the null hypothesis and reject the alternative hypothesis
- chance is a likely explanation of study finding.
what is type I error?
when the study finds a significant result when there truly isn’t one (null hypothesis is true)
when is risk of type I error reduce?
when small p values are used
what is type II error?
when you don’t find a statistically significant result when there truly is one
(alternative hypothesis is true and there is statistically significant association)
when is type II error more likely?
with small sample size
what type of clinical importance and statistical significance are the points labelled A-E on the graph?
A - not clincally important, not statistically significant
B - statistically significant, not clincally important
C - statistically significant, possibly clinically important
D - not statistically significant, possible clincally important
E - statistically significant, clinically important
