Ethics & Statistics

Question 1

Elizabeth Kubler-Ross psychological stages at the end of life

Answer 1

Denial, anger, bargaining, depression, & acceptance

Question 2

Sensitivity

Answer 2

the probability that a person w/ a disease will have a positive result on a given test
***high sensitivity is useful in a screening test, as the goal is to identify everyone w/ a given disease

Question 3

Specificity

Answer 3

the probability that a person w/o a disease will have a negative result on a test
***high specificity is desirable for a confirmatory test

Question 4

positive predictive value (PPV)

Answer 4

the probability that a person with a positive test result has the disease (true positives/all positives); if a disease has a greater prevalence, then the PPV is higher

Question 5

negative predictive value (NPV)

Answer 5

the probability that a person w/ a negative test result is disease free (true negatives/all negatives); a test has a higher NPV when a disease has a lower prevalence

Question 6

incidence

Answer 6

the number of NEW cases of a given disease per year

Question 7

prevalence

Answer 7

the total number of EXISTING cases of a given disease in the entire population

Question 8

absolute risk

Answer 8

the probability of an event in a given time period

Question 9

relative risk

Answer 9

used to evaluate results of cohort (prospective) studies; compares the incidence of a disease in a group exposed to a particular risk factor (RF) w/ the incidence in those not exposed to the RF; an RR 1 means that the event is more likely in that group

Question 10

odds ratio

Answer 10

used in case-control (retrospective) studies; compares rate of exposure among those w/ & w/o disease; considered less accurate than RR

Question 11

Absolute risk reduction (ARR) or attributable risk

Answer 11

measures risk accounted for by exposure to a given factor, taking into account the background of the disease; useful in RCTs; numerically, ARR=the absolute risk (rate of adverse events) in placebo group minus absolute risk in treated pts

Question 12

relative risk reduction (RRR)

Answer 12

used in RCTs; the ratio between 2 risks; numerically, RRR=[the event rate in control pts minus event rate in experimental pts] divided by the event rate in control pts
***can be deceptive & is clinically far less important than ARR

Question 13

number needed to treat (NNT)

Answer 13

the number of pts who would need to be treated to prevent 1 event; NNT=1/ARR

Question 14

statistical significance/p-value

Answer 14

expresses likelihood that an observed outcome was due to random chance; a p-value <0.05 is gen. accepted as indicating that an outcome is statistically significant

Question 15

confidence interval (CI)

Answer 15

like the p-value, expresses certainty that observation is real or is a product of random chance; used with ORs & RR, the 95% CI says that the observed risk or odds have a 95% chance of being w/in the interval
***if a 95% CI includes 1.0, the results are NOT significant

Question 16

cohort study

Answer 16

a population is observed over time, grouped on the basis of exposure to a particular factor, & watched for a specific outcome

• not good studies for rare conditions
• can be prospective or retrospective
• use RR to interpret results

Question 17

case-control study

Answer 17

a retrospective study involving a group of people w/ a given disease & an otherwise similar group of people w/o disease who are compared for exposure to RFs; good for rare diseases; use OR to interpret results

Question 18

randomized controlled trial (RCT)

Answer 18

a prospective study that randomly assigns participants to a treatment group or to a placebo group; the placebo group & treatment group are then compared to determine if the treatment made a difference
*the double-blind RCT is the gold standard of experimental design

Question 19

Standardized mortality ratio (SMR)

Answer 19

Represents an adjusted measure of overall mortality and is calculated by dividing the observed number if deaths in the population of interest by he expected number derived from the reference population; mortality is typically adjusted for age and less commonly for gender, race, etc.

Question 20

Bell curves and standard deviations

Answer 20

In a normal (bell-shaped) distribution curve, 68% of observations lie w/in 1 SD of the mean, 95% w/in 2 SDs, and 99.7% w/in 3 SDs