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Statistics
Statistical Calculations
19
Pharmacology
Post-Graduate
04/15/2013

Additional Pharmacology Flashcards

 


 

Cards

Term
p-value measures
Definition
The likely hood that the null hypothesis is true.
Term
Type 1 error
Definition
A false positive.  Or you deny the null hypothesis when it is true.  Or you find a significant difference when there isn't one.
Term
Type II error
Definition
A false negative.  Accepting the null hypothesis when it is false.  Or not finding a significant difference when there really is one.
Term
Statistical power (B)
Definition
The probibility the test will reject the the null hypothesis when it is false.  So probability you will not make Type II error.  The power is usually .8.  Power increases with increased participants or events.  Themore participants you have the more likely you are to see a difference if there is one is how I look at it.
Term
Relative Risk definition
Definition
Probability of an event occurring in the exposed group vs.  a non-exposed (or control) group.  A relative risk of 1 indicates no difference between comparison groups. A
RR < 1 means that the intervention reduced the risk of the outcome.
Term

Relative Risk calculation

 

if disease progression occurred in 28% of placebo-treated
patients and in 16% of metoprolol-treated patients what is the relative risk

Definition
Relative risk is 16/28 or 0.57.  So patients treated with metoprolol were 57% as likely to have disease progression compared to placebo.
Term

Relative Risk Reducation calculation 

 

if disease progression occurred in 28% of placebo-treated
patients and in 16% of metoprolol-treated patients, what is the relative risk reduction

Definition

Relative risk reduction = 1- relative risk

 

Relative risk = 16/28 = 0.58

 

1-0.58 = 0.42

 

meaning there is a 42% risk reduction in disease progression in patients being treated with metoprolol

 

Not the best for measuring clinical significance.  For example if the disease progession happened to 4% of patients in placebo and 2% in metoprolol group the relative risk reduction would be 50% but is this just 2% difference clinically significant.  For clinically significant absolute risk reduction is best

Term
Absolute Risk Reduction definition
Definition
absolute difference in outcome rates between the treatment and control groups
Term

Absolute Risk Reduction calculation

 

if disease progression occurred in 28% of placebo-treated
patients and in 16% of metoprolol-treated patients what is the absolute risk reduction?

Definition
28-16% = 12% absolute risk reduction
Term
Number needed to treat definition
Definition
represents the number of people who would need
to be treated with the intervention in order to prevent 1 adverse event
Term

number needed to treat (NNT) calculation

 

if disease progression occurred in 28% of placebo-treated
patients and in 16% of metoprolol-treated patients.  What is the number needed to treat?

Definition

NNT = 1/absolute risk reduction

 

Absolute risk reduction = 28-16% = 12%

 

1/0.12 = 8.3

 

NNT = 9 patients (round up)

Term
Odds ratio definition
Definition
ratio of the odds of an event occurring in the treatment group to the odds of an event occurring in the control group
Term

Odds ratio calculation

 

In a group of 100 smokers, 40 people developed
lung CA while 60 people do not. In a similar group of 100 non-smokers, lung CA developed in 10 people. What is the odds ratio?

Definition

The odds of a smoker developing lung CA would be 40/60 = 0.66 (number of people that had the event over number of people that did not), whereas  the odds of a non-smoker developing lung CA would be 10/90 = 0.11

 

The odds ratio would then be 0.66/0.11 = 6

 

If the odds ratio is close to 1 then there is not much different between the 2 groups

 

Term
Discrete data definition
Definition
Discrete data has a limited number of values usually within categories or classifications.  Descrete data can be ordinal or nominal data.
Term
Ordinal data definition
Definition

Subtype of discrete data,  assigned numbers have meaningful order but not necessarily an equal distance between them.

 

Ex.  No pain, mild pain, moderate pain, severe pain

 

Term
Nominal Data definition
Definition

Subtype of discrete data.  Categories have no rank or order. 

 

Ex.  male/female, Yes/no

 

 

Term
Continuous data definition
Definition
Values are within a defined range.  Equal distance between values.  Broken down into ratio and interval data
Term
Ratio data definition
Definition

Subtype of continuous data.  Has an absolute zero.

 

Ex.  Height, age, blood pressure

Term
Interval data definition
Definition

It has no absolute zero.

 

Ex.  Temperature in Fahrenheit or celcius (Kelvin has absolute zero)

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