Evidenced Based Dentistry 1

Question 1

what is the definition of risk

Answer 1

what are the chances

can be good or bad

Question 2

what is the definition of outcome

Answer 2

something that might happen

Question 3

what are statistics

Answer 3

numbers that summarize information

Question 4

what are statistics based on

Answer 4

observations of large numbers of people

Question 5

what are statistics useful for

Answer 5

predicting what is likely to happen in the future

Question 6

what does the numerator represent

Answer 6

number of people who actually experience the outcome

Question 7

what does the denominator represent

Answer 7

the number of people who could potentially experience the outcome

Question 8

what are risks and odds

Answer 8

just ways of expressing chance in numbers

for binary events they just express the chance of being in one of the two states

Question 9

how do you calculate risk

Answer 9

number of events of interest/total number of observations

Question 10

how do you calculate odds

Answer 10

number of events of interest/number without the event

Question 11

what are the questions to ask when interpreting risk

Answer 11

risk of what - what is the outcome?
how big is the risk - what are the chances of experiencing the outcome, what timeframe?
does the risk information reasonably apply to me or my patient?
how does this risk compare with others risks - should i do something about this risk

Question 12

what are the questions to ask about risk reduction

Answer 12

reduced risk of what?
how big is the risk reduction?
does the risk reduction info reasonably apply to me?
any downsides?
is the benefit (risk reduction) worth the downsides?

Question 13

what is the difference between the relative risk reduction and absolute risk reduction

Answer 13

relative risk reduction makes even small risk reductions sound big making us overestimate the benefits

Question 14

what is the number needed to treat

Answer 14

the number of patients you would need to treat to prevent one patient from developing the disease/condition/outcome

Question 15

what is a confidence interval

Answer 15

a confidence interval tells us the range of values that a true population treatment effect is likely t lie

Question 16

describe what confidence intervals show

Answer 16

a CI that embraces/overlaps/contains/straddles the ‘value of no difference’ between treatments indicates that there is insufficient evidence for a difference between the treatment and control group in the population

Question 17

what is the ratio value for confidence intervals

Answer 17

if the confidence interval embareces 1 then there is insufficient evidence
if this interval does not embrace 1 then there is sufficient evidence to suggest a difference

Question 18

if two values are equal what is the value of no difference

Answer 18

0
there is sufficient evidence for a difference between two values in the population if the CI for the difference does not overlap 0

Question 19

if two values are equal in a ratio what is the value of no difference

Answer 19

1

sufficient evidence for a difference between two values in the population if the CI for the ratio does not overlap 1

Question 20

what are the different study designs in human research

Answer 20

observational uncontrolled studies
controlled studies
randomized controlled trials

Question 21

what are observational uncontrolled studies

Answer 21

researchers watch what happens to a group of people

Question 22

what are controlled studies

Answer 22

cohort or case control

researchers observe what happens to people in different situations without intervening

Question 23

what are randomized controlled trials

Answer 23

patients randomly split into 2 groups - one gets intervention and the other placebo
any differenced at follow-up caused by intervention

Question 24

what is a case report/case series

Answer 24

a report on a single patient or series of patients with an outcome of interest - no control group is involved

Question 25

what is a case report/case study used for

Answer 25

identify the new disease outcome

hypothesis generation

Question 26

what are the disadvantages of a case study

Answer 26

cannot demonstrate the valid statistical associations

lack of control group

Question 27

what are cross sectional studies

Answer 27

the observation of a defined population at a single point in time - or time interval
exposure and outcome are determined at the same time

Question 28

what are cross sectional studies used for

Answer 28

estimating prevalence of a disease

investigate potential risk factors

Question 29

what are the disadvantages of cross sectional studies

Answer 29

causality
confounding
recall bias

Question 30

what is a case control study

Answer 30

the study of people with a disease and a suitable control group of people without the disease
looks back in time at exposure to a particular risk factor in both groups

Question 31

what is a case control study used for

Answer 31

looking at potential causes of disease

Question 32

what are the disadvantages of case control study

Answer 32

confounding 
recall/selection bias
selection of controls
time relationships (did exposure occur before disease)

Question 33

what is a cohort study

Answer 33

establish a group of individuals in population
measure exposures
follow up over a period of time
identify those that develop disease (outcome of interest)

Question 34

what is a cohort study used for

Answer 34

estimating incidence of disease
investigating causes of disease
determining prognosis
timing and direction of events

Question 35

what are disadvantages of cohort studies

Answer 35

controls difficult to identify 
confounding
blinding difficult
for rare diseases - need large samples
very expensive/time consuming

Question 36

what are randomized controlled trials

Answer 36

sometimes referred to as a clinical standard
considered the gold standard
for effectiveness and efficiency
particularly useful for clinical studies
provides strongest evidence on effectiveness of treatments

Question 37

what are the 4 design elements of RCT

Answer 37

specification of participants (inclusion/exclusion criteria)
control/comparison groups
randomisation
blinding/masking

Question 38

what are the inclusion/exclusion criteria

Answer 38

unambiguous

exact definitions

Question 39

what is the comparison groups

Answer 39

placebo

current standard treatment

Question 40

what is randomization

Answer 40

how participants/subjects/patients are allocated to treatments

Question 41

why is randomization done

Answer 41

eliminate bias

Question 42

how should randomization be done

Answer 42

by a computer

Question 43

what is blinding/masking

Answer 43

if the participant or researcher is unaware of which treatment is given it may influence the results

Question 44

what may change if participant/researcher is aware of which treatment is being given

Answer 44

participant
administrator of treatment
assessor of outcome
data analyst

Question 45

what are the advantages of RCTs

Answer 45

provide strongest and most direct epidemiological evidence for causality
but non blinded RCTs may overestimate effects

Question 46

what are disadvantages of RCTs

Answer 46

more difficult to design and conduct than observation studies due to ethical issues, feasibility, costs
still some risk of bias and generalizability often limited
not suitable for all research questions