Use of stats for IP

Question 1

Rate formula

Answer 1

X/Y *K

Question 2

Measure of the frequency of death in a defined population during a specified time (usually a year)

Answer 2

Mortality rate

Question 3

Measures the proportion of the population dying each year from all causes

Answer 3

crude mortality rate

Question 4

Measures mortality from a specified cause for a population

Answer 4

cause-specific mortality rate

Question 5

crude rate k

Answer 5

1000

Question 6

cause specific rate k

Answer 6

100,000

Question 7

Summary measure that compares HAI rates over time among one or more groups of patients to that of a standard population

Answer 7

Standardized Infection Ration (SIR)

Question 8

Who calculates SIR?

Answer 8

NHSN

Question 9

True or false: each SIR is procedure specific and based on specific patient risk factors

Answer 9

True

Question 10

What does the standardized infection ration (SIR) measure?

Answer 10

How a single hc facility’s infection rates differ from a national standard

Question 11

calculation for SIR

Answer 11

Observed # of infections/ expected # of infections

Question 12

how to interpret an SIR

Answer 12

SIR =1: the facility’s rates are the same as expected by the NHSN benchmark

SIR >1: Facility’s rates are higher than the NHSN benchmark

SIR <1: Facility’s rates are better than the NHSN benchmark

Question 13

Measure of the strength of association used in prospective and experimental studies

Answer 13

relative risk

Question 14

equation for relative risk

Answer 14

Probability of developing disease if the risk factor is present / probability of developing disease if risk factor is not present

Question 15

what does relative risk estimate?

Answer 15

how much more likely disease is to occur in exposed groups compared to unexposed ones

Question 16

what studies are relative risk (risk ratio) used for?

Answer 16

cohort

Question 17

What question does relative risk answer?

Answer 17

what is the risk of developing disease if exposed to the risk factor?

Question 18

Interpreting the risk ratio

Answer 18

RR=1: there is no significant association
RR>1: there is a positive association
RR<1: there is a negative association (protective)

Question 19

Measure of association- the probability of having a particular risk factor if a condition or disease if condition is present

Answer 19

Odds Ratio

Question 20

Calculation for odds ratio

Answer 20

Probability of having risk factor if disease present/ probability of having risk factor if disease is not present

Question 21

Types of studies for odds ratios

Answer 21

Case control
cross-sectional studies

Question 22

Is OR appropriate for chronic diseases?

Answer 22

No, because it looks at prevalence not incidence

Question 23

What question does the odds ratio ask?

Answer 23

If the disease is present, what is the likelihood of having been exposed to the risk factor?

Question 24

Used to calculate the direction and magnitude of a relationship between two variables

Answer 24

Correlation

Question 25

What is the value calculated for correlation?

Answer 25

r

Question 26

range for correlation

Answer 26

-1 to 1

Question 27

positive correlation

Answer 27

as one variable increases, so does the other

Question 28

Negative correlation

Answer 28

as one variable increases, the other decreases

Question 29

Strength of association- r=1 or r=-1

Answer 29

strong association

Question 30

Strength of association: r=0

Answer 30

Weak or no correlation

Question 31

Can a normal distribution be assumed for day to day surveillance and data collection?

Answer 31

No because sample sizes usually small

Question 32

This type of testing estimates the likelihood that a result did not occur by chance

Answer 32

Hypothesis testing

Question 33

Rejecting the Ho when it is true

Answer 33

Type 1 error

Question 34

what is the probability of a type 1 error?

Answer 34

p-value

Question 35

Null hypothesis is false and you accept it

Answer 35

Type II error

Question 36

The probability of getting unusual results

Answer 36

P-value