NNT (number needed to treat)
The number of people you would have to treat to prevent one adverse outcome.
Relative Risk (RR)
How many times more likely one group is to have an outcome compared to another group.
Incidence: the rate of new cases of a disease
The proportion of the population that could be affected by a disease that is affected by a disease.
How good a test is at calling true positives positive (the true positive rate)
Sn= true positives/all those who have the disease
How good a test is at calling negative those who are actually negative (the true negative rate)
Sp= true negatives/ all those who don't have the disease
Positive predictive value (PPV)
If someone has a positive test result, the percent chance that they are actually positive
PPV= true positives/all positive results
***N.B: depends on prevelance. As the disease prevelance goes down, the PPV goes down***
Negative predictive value (NPV)
If someone has a negative test result, the percent chance they are truly negative
NPV= true negatives/all negative test results
****NB depends on prevalence. As prevalence of a disease goes down, the NPV goes up***
Absolute risk reduction (ARR)
EER= exposed event rate= # events/# ppl in exposure group
CER= control event rate= #events/# ppl in control group
What do confidence intervals tell us?
Tell us if something is statistically significant (the confidence interval does not include zero if you are looking at a difference, and does not include 1 if you are looking at an OR or RR) and the precision of the study (good precision=narrow interval)
The number of people correctly classified using a test (true positives + true negatives/all test results)
What does a P-value tell you?
It is the probability that the event occured by chance.
Likelihood ratio for a positive test
How much more likely a positive test result is in someone with as opposed to without the condition
(probability of an individual with the disease testing positive)/(probability of an individual without the disease testing positive)
Likelyhood ratio for a negative test
How much more likely a negative test result is to be found in a person with vs. without the disease
(probability of an individual with the disease testing negative)/(probability of an individual without the disease testing negative)
Relative risk reduction
EER= exposed event rate= #events/#ppl in exposed group
CER= control event rate= # events/#ppl in control group
A study where a variable is manipulated is called _____ and a study where variables are not manipulated are called_____
Experimental (e.g. RCTs)
Obersvational (e.g. case reports, case-control, cross-sectional, cohort)
What are a few defining differences between quantitative research and qualitative research?
- generates hypotheses (inductive)
- asks open-ended questions
- data=text, images...
- answers "why?"
- answers hypotheses (dedcutive)
- asks closed ended questions
- data= numbers etc..
- answers "why?, how much?"
How do you use likelihood ratios to predict whether or not a person has a disease?
You need to use a nomogram. Pre-test probability is estimated or you can use the prevalence and combined with the LR+ or LR- (depending on whether they have a positive or a negative test result) to give a post-test probability.
Used in case-control studies.
OR= [(ill+exposed)/(ill+unexposed)]/[(not ill+exposed)/(not ill +not exposed)]
What is type 1 error?
Rejecting the null hypothesis when the null hypothesis is true (alpha)
What is type 2 error?
Failing to reject the null hypothesis when the null hypothesis is false.
Draw the hypothesis testing table