# Lecture 3 Flashcards

1
Q

risk

A
• the probably that the outcome will occur given a particular set of circumstances
• also called measures of association
2
Q

risk difference

A
• the risk (incidence) of disease in one group minus the risk (incidence) of disease in another group
3
Q

attributable risk

A
• risk difference when referring to factors that increase the risk of disease
• I_E-I_U
```I_E = incidence in exposed
I_U = incidence in unexposed```
4
Q

attributable risk percent

A
• the percent of the risk in the exposed group that is attributable to the exposure
• percentage of risk among the exposed group that would be eliminated if the exposure had not occurredI_E-I_U
________
I_E
5
Q

absolute risk reduction

A
• the proportion of patients who were spared an adverse outcome due to the treatment

I_C - I_Rx

I_C=incidence in control group
I_Rx=incidence in treated group

6
Q

relative risk

A
• the probability of an outcome given an exposure (risk factor or treatment) compared to the risk without the exposure

RR = I_E/I_U OR
I_Rx/I_C for treatment

7
Q

when the relative risk is greater than 1.0

A
• the exposure or treatment increases the risk of disease
8
Q

when the relative risk is less than 1.0

A
• the exposure or treatment decreases the risk of disease
9
Q

when the relative risk = 1.

A
• the exposure or treatment does not increase or decrease the risk of disease
10
Q

relative risk reduction

A
• the percentage of baseline risk that is removed as a result of a given therapy

RRR = ARR/I_c = (I_c - I_Rx)/I_c

RRR=1-RR

11
Q

number needed to treat

A
• how many patients need to be treated to prevent one outcome event

NNT = 1/ARR

12
Q

standard deviation

A
• a measure of the degree of variability in individual measurements in a study
• how much variability there is in measurements from individuals in a sample
13
Q

for a variable that is distributed normally

A
• 68% of the values will be between one standard deviation

95% will be between two standard deviations

14
Q

standard error

A
• a measure of the dispersion of a sample means around the population mean
• how much uncertainty there is in the group values

standard error = SD/ sqrt (sample size)

15
Q

null hypothesis

A
• there is no difference in outcomes between comparison populations
• Ho is never accepted
16
Q

type I error

A
• incorrectly concluded that there is a difference when there is not
• alpha
17
Q

type II error

A
• fail to find a difference when a true difference exists

- false negative

18
Q

p value

A
• the probability of finding an outcome as extreme as or more extreme than the one we found, assuming that the null hypothesis is true
19
Q

the lower the p value

A
• the less compatible the data are with the null hypothesis
20
Q

The greater the test statistic

A
• the lower the p value
21
Q

the lower the test statistic

A
• the greater the p value
22
Q

limitations of p values

A
• mix together
• size of an effect
• sample size
• variability of the data
23
Q

point estimate

A
• the specific numeral result of a study
24
Q

confidence interval

A
• the calculated range of values surrounding the point estimate that are consistent with the true effect
25
Q

if null value is outside of the 95% confidence interval

A

p < 0.05

26
Q

if the null value is within the confidence interval

A

p > 0.05

27
Q

values near the point estimate

A
• more consistent with the population value
28
Q

values near the limits of the confidence

A
• less consistent with the population value
29
Q

degree of precision of an estimate

A
• indicated by the width of the confidence interval
30
Q

the narrower the confidence interval

A
• the more precise the estimate
31
Q

statical power of a study

A
• the study’s ability to detect a difference assuming that a real difference exists
• the probability of not making a type II error
32
Q

clinical importance

A
• the salience of a finding for clinical practice
• related to the magnitude (size) of the finding
• taking into account the seriousness of the outcome, and the prevalence of the condition