chapter 44: statistics and patient safety

Question 1

rejects null hypothesis incorrectly -> falsely assumed there was a difference when no difference exists

Answer 1

type 1 error

Question 2

rejects null hypothesis incorrectly -> falsely assumed there was a difference when no difference exists

Answer 2

type 1 error

Question 3

accepts null hypothesis incorrectly because of small sample size -> the treatments are interpreted as equal when there is actually a difference

Answer 3

type 2 error

Question 4

hypothesis that no difference exists between groups

Answer 4

null hypothesis

Question 5

p value that rejects the null hypothesis

Answer 5

p

Question 6

p value: > 95% likelihood that the difference between the populations is true

Answer 6

p

Question 7

likelihood that the difference is not true and occurred by chance alone with p

Question 8

spread of data around a mean

Answer 8

variance

Question 9

population

Answer 9

parameter

Question 10

most frequently occurring value

Answer 10

mode

Question 11

average

Answer 11

mean

Question 12

middle value of a set of data

Answer 12

median

Question 13

prospective study with random assignment to treatment and non treatment groups

Answer 13

randomized controlled trial (avoids treatment biases)

Question 14

prospective study in which patient and doctor are blind to the treatment

Answer 14

double-blind controlled trial

- avoids observational bias

Question 15

prospective study -> compares disease rate between exposed and unexposed groups (nonrandom assignment)

Answer 15

cohort study

Question 16

retrospective study in which those who have the disease are compared with a similar population who do not have the disease; the frequency of the suspected risk factor is then compared between the 2 groups

Answer 16

case-control study

Question 17

combining data from different studies

Answer 17

meta-analysis

Question 18

2 independent groups and variable is quantitative -> compares means (mean weight between 2 groups)

Answer 18

student’s t test

Question 19

variable is quantitative; before and after studies (e.g. weight before and after, drug versus placebo)

Answer 19

paired t tests

Question 20

compares quantitative variables (means) for more than 2 groups

Answer 20

ANOVA

Question 21

compare categorical (qualitative) variables (race, sex, medical problems and diseases, medications)

Answer 21

nonparametric statistics

Question 22

compares 2 groups with categorical (qualitative) variables (number of obese patients with and without diabetes versus number of non obese patients with and without diabetes)

Answer 22

chi-squared test

Question 23

small groups -> estimates survival

Answer 23

Kaplan-Meyer

Question 24

incidence in exposed / incidence in unexposed

Answer 24

relative risk

Question 25

probability of making the correct conclusion = 1 - probability of type 2 error - likelihood that the conclusion of the test is true - larger sample size increases power of a test

Answer 25

power of test

Question 26

number of people with disease in a population (Eg number of patents in US with colon CA) - long-standing disease increases prevalence

Answer 26

prevalence

Question 27

number of new cases diagnosed over a certain time frame in a population (e.g. number of patients in the US newly diagnosed with colon CA in 2003)

Answer 27

incidence

Question 28

ability to detect disease = true-positives/(true-positives+false-negatives) - indicates the number of people who have the disease who test positive

Answer 28

sensitivity with high sensitivity, a negative test result means patient is very unlikely to have disease

Question 29

ability to state no disease is present = true-negatives/(true-negatives + false-positives) - indicates the number of people who do not have the disease who test negative

Answer 29

specificity with high specificity, a positive test result means patient is very likely to have disease

Question 30

true-positives / (true-positive + false-positive) | - likelihood that with a positive result, the patient actually has the disease

Answer 30

positive predictive value

Question 31

true-negatives / (true-negatives + false-negatives) | - likelihood that with a negative result, the patient does not have the disease

Answer 31

negative predictive value

Question 32

depends on disease prevalence

Answer 32

predictive value

Question 33

depends on disease prevalence

Answer 33

predictive value

Question 34

accepts null hypothesis incorrectly because of small sample size -> the treatments are interpreted as equal when there is actually a difference

Answer 34

type 2 error

Question 35

hypothesis that no difference exists between groups

Answer 35

null hypothesis

Question 36

p value that rejects the null hypothesis

Answer 36

p

Question 37

p value: > 95% likelihood that the difference between the populations is true

Answer 37

p

Question 38

likelihood that the difference is not true and occurred by chance alone with p

Answer 38

less than 5%

Question 39

spread of data around a mean

Answer 39

variance

Question 40

population

Answer 40

parameter

Question 41

most frequently occurring value

Answer 41

mode

Question 42

average

Answer 42

mean

Question 43

middle value of a set of data

Answer 43

median

Question 44

prospective study with random assignment to treatment and non treatment groups

Answer 44

randomized controlled trial (avoids treatment biases)

Question 45

prospective study in which patient and doctor are blind to the treatment

Answer 45

double-blind controlled trial | - avoids observational bias

Question 46

prospective study -> compares disease rate between exposed and unexposed groups (nonrandom assignment)

Answer 46

cohort study

Question 47

retrospective study in which those who have the disease are compared with a similar population who do not have the disease; the frequency of the suspected risk factor is then compared between the 2 groups

Answer 47

case-control study

Question 48

combining data from different studies

Answer 48

meta-analysis

Question 49

2 independent groups and variable is quantitative -> compares means (mean weight between 2 groups)

Answer 49

student's t test

Question 50

variable is quantitative; before and after studies (e.g. weight before and after, drug versus placebo)

Answer 50

paired t tests

Question 51

compares quantitative variables (means) for more than 2 groups

Answer 51

ANOVA

Question 52

compare categorical (qualitative) variables (race, sex, medical problems and diseases, medications)

Answer 52

nonparametric statistics

Question 53

compares 2 groups with categorical (qualitative) variables (number of obese patients with and without diabetes versus number of non obese patients with and without diabetes)

Answer 53

chi-squared test

Question 54

small groups -> estimates survival

Answer 54

Kaplan-Meyer

Question 55

incidence in exposed / incidence in unexposed

Answer 55

relative risk

Question 56

probability of making the correct conclusion = 1 - probability of type 2 error - likelihood that the conclusion of the test is true - larger sample size increases power of a test

Answer 56

power of test

Question 57

number of people with disease in a population (Eg number of patents in US with colon CA) - long-standing disease increases prevalence

Answer 57

prevalence

Question 58

number of new cases diagnosed over a certain time frame in a population (e.g. number of patients in the US newly diagnosed with colon CA in 2003)

Answer 58

incidence

Question 59

ability to detect disease = true-positives/(true-positives+false-negatives) - indicates the number of people who have the disease who test positive

Answer 59

sensitivity with high sensitivity, a negative test result means patient is very unlikely to have disease

Question 60

ability to state no disease is present = true-negatives/(true-negatives + false-positives) - indicates the number of people who do not have the disease who test negative

Answer 60

specificity with high specificity, a positive test result means patient is very likely to have disease

Question 61

true-positives / (true-positive + false-positive) | - likelihood that with a positive result, the patient actually has the disease

Answer 61

positive predictive value

Question 62

true-negatives / (true-negatives + false-negatives) | - likelihood that with a negative result, the patient does not have the disease

Answer 62

negative predictive value

Question 63

true-positives + true-negatives / true-positives+true-neg+false-pos+false-neg

Answer 63

accuracy

Question 64

depends on disease prevalence

Answer 64

predictive value

Question 65

are independent of prevalence

Answer 65

sensitivity and specificity

Question 66

seeks to collect outcome date to measure and improve surgical quality in the US. outcomes are reported as observed vs expected ratios

Answer 66

National Surgery Quality Improvement Program (NQSIP)

Question 67

JCAHO prevention of wrong site/procedure/patient protocol

Answer 67

- preop verification of patient and procedure - operative site and side - time out before incision is made (verifying patient, procedure, position site + side, and availability of implants or special requirements)

Question 68

promoting culture of safety

Answer 68

- confidential system of reporting errors - emphasis on learning over accountability - flexibility in adapting to new situations or problems

Question 69

risk factors for retained object after surgery (MC sponge)

Answer 69

emergency procedure, unplanned change in procedure, obesity, towel used for closure

Question 70

unexpected occurrence involving death or serious injury, or the risk thereof; hospital undergoes root cause analysis to prevent and minimize future occurrences (Eg wrong site surgery)

Answer 70

sentinel event (JCAHO)

Question 71

GAP protection technique

Answer 71

gaps in care (shift change, etc) can lead to loss of information and error. prevention - structured handoffs and checklists (face to face if possible; standardizing orders; reading back orders if verbal