BIOL 437 Week Nine p.1 (Experimental Studies)

Question 1

epidemiologic experimental studies

Answer 1

-resemble contorlled experiments performed in scientific research
>repeatable
>evaluate effects of assigned intervetnsions on an outcome

Question 2

epi experimental studies best for

Answer 2

• relatively mature quesitons
  1. Establishing cause-effect relationships
  2. Evaluating the efficacy of prevention and therapeutic interventions

Question 3

experimental studies

Answer 3

• intervention studies
• investigators influence exposure of study subjects
• uses comparision group

Question 4

“gold standard”

Answer 4

-experimental studies
>random assignment
>blinding

Question 5

2 types of experimental trials

Answer 5

1. Controlled trials

2. Community trials

Question 6

controlled trial

Answer 6

• invidividual
  ex. randomized control trial
  1. Prophylactic trial
  2. Therapeutic trial

Question 7

clinical trial

Answer 7

-randmoized controlled trial in a clinical setting

Question 8

trial

Answer 8

-each replication of an experiment that can be repeated

Question 9

prophylactic trial

Answer 9

-to evaluate preentive measures

Question 10

therapeutic trial

Answer 10

-to assess new treatment methods

Question 11

community trial

Answer 11

• group or community
• where 1 group receives an intervention but the other does not
• quasi- experimental designs

Question 12

group intervention

Answer 12

-designed for purpose of education and behavioural changes at population level

Question 13

quasi-experimental designs

Answer 13

• manipulation of study factors, but do not assign intervention randomly
• need a large enough group being randomly assigned to minimize confounding factors

Question 14

experimental studies may be

Answer 14

• between-group designs

- within-group designs

Question 15

between-group designs

Answer 15

• strongest methodoloical design

- outcomes compared between 2 or more groups receiving different levels of the intervention

Question 16

within-group design

Answer 16

-outcome in single group is compared before and after the assignment of an intervention

Question 17

within-group strength

Answer 17

-individual characteristics that might confound an association are controlled (ex. gender, race)

Question 18

within-group weakness

Answer 18

-susceptible to confounding from time-related factors but may be adjusted for in the analysis (ex. media)

Question 19

natural experiment

Answer 19

• rare situations in nature where unplanned events produce an experiment
• ex. screening and treatment for prostate cancer

Question 20

random assignment

Answer 20

• makes intervention and contorl groups look as similar as possible
• chance is the only factor that determines group assignment
• minimize potential influnce of confounding factors
• can apply inferential stats tests of probability and determine levels of significance
• eliminate bias
• most common type of clinical trials

Question 21

non-randomized study

Answer 21

• convenience sample

- concurrent comparison group allocated by a non-random process

Question 22

problems of non-random

Answer 22

• not effective at controlling unmeasured confounding variables
• measured confounding variables may be adjusted through analytical methods

Question 23

reasons to use non-random

Answer 23

• large research population not always available
• lack of participants with disease/condition
• lack of desire to participate
• when entire population subjected to a treatment

Question 24

advantages of randomization

Answer 24

• eliminates conscious bias due to physician or patient selection
• averages out unconsious bias due to unknow factors
• groups are ‘alike on average’

Question 25

disadvantages of randomization

Answer 25

• ethical issues

- interfers with the doctor-patient relationship

Question 26

blinding

Answer 26

-used to minimize potenital bias from placebo effect

Question 27

placebo

Answer 27

-a substance containing no medication or treatment given to satisfy a patient’s expectation to get well

Question 28

3 levels of blinding

Answer 28

1. Single blind: subjects
2. Double blind: subjects and investigators
3. Triple blind: subjects and investigators and analysers

Question 29

why blind patients?

Answer 29

• patients try to get well/please physicians
• minimize potential bias from a placebo effect
• related to whether outcome is subjectively determined
  (ex. pain releif vs. blood test)

Question 30

placebo effect

Answer 30

-effect on patient outcomes that may occur due to the expectation by a patient that a particular intervention will have an effect

Question 31

problems with blinding

Answer 31

in non-drug studies may be impossible or unethical (ex. sham operation)
-in drug studies if treatment has characteristic side effects (ex. frequent urination)

Question 32

placebos improve

Answer 32

-compariability of treatment groups in terms of compliance and follow-up

Question 33

blinding physician or investigator

Answer 33

• best way to avoid bias

- may not always be possible

Question 34

purpose of experimental studies

Answer 34

• to identify clinical and public health approaches to solving public health problems
• how to prevent or treat

Question 35

strengths of blinded, randomized controlled clinical trials

Answer 35

• demostrate cause-effect relationship
• may produce faster and cheaper answer
• only appropriate approach for some research questions
• allow investigators to contorl exposure levels as needeed

Question 36

weaknesses of blinded randominzed controlled clinical trials

Answer 36

• more costly in time and money
• many questions aren’t suitable due to ethical barriers
• many questions not suitable for blinding
• standardized interventions may be different from common practice
• limited generalizability due to volunteers, eligibility criteria and loss to follow up