EAB - study design and summarising data Flashcards
What is an RCT?
- Intervention study
- Choice of treatment/intervention allocated randomly
- Typically randomised to new vs current or placebo treatment
Why do we need to randomise in RCTs?
- Ensures patients’ characteristics don’t affect which treatment they receive
- Unbiased
- Treatment groups balanced
- Any differences in outcome can be attributed to treatment
- Fair test of efficacy
- Usually use computer-generated random list
what is the gold standard for research studies
RCT
What are 2 limitations of RCTs?
- Can be expensive and difficult to organise
- Some interventions are impossible or unethical to randomise to
- ## e.g. impact of lead on children’s intelligence
What are cohort studies?
- Observational study - no intervention
- Subjects observed in natural state (real world)
- Investigates causes or factors associated with disease (or condition)
- Selects group of healthy individuals
- Follow-up to monitor disease state and possible risk factors over time
- Disease state (e.g. yes/no) according to risk factor status (e.g.
smoking yes/no) - Usually prospective (but retrospective designs may be used)
What are the advantages of cohort studies?
- Data is collected prospectively, so estimates are less likely to be biased than those from a case-control
- RCTs can only investigate potential benefits for ethical reasons
- Imbalance between exposed and unexposed can be corrected
- Cohort studies can look at exposure to treatment and harm
eg impact of lead on children’s intelligence
What are case control studies?
- Observational study - no intervention
- Subjects observed in natural state (real world)
- Investigates causes or factors associated with disease (or condition)
- Selects group with disease: ‘cases’
- Choose comparator group without disease: ‘controls’
- Compare cases and controls with respect to possible risk factors
- Usually retrospective
What are the limitations of a case-control study?
x Choice of control group affects comparison
x Data reported by subjects or from records - usually retrospective so may be incomplete, inaccurate or biased
what are advantages of case control studies
✓ BUT often quick to do and inexpensive!
✓ Evidence from case-control studies may be used in planning further research
What are cross-sectional studies?
- Observational study
- Subjects observed in natural state (real world)
- Collect data for each subject at one point in time only
- Similar to a cohort study, but without follow-up
What are the limitations of cross-sectional studies?
- Useful for:
*measuring prevalence of a disease/condition- e.g. % in population with asthma - surveys of attitudes/views/behaviours -e.g. patient satisfaction, alcohol drinking
- Not useful for looking at cause & effect
out of RCT, case control, cohort, and cross sectional, which one is intervention and which one is observational?
RCT = intervention
CROSS SECTION, COHORT, CASE CONTROL = observational
What are 2 types of quantitative data?
- Continuous: lies on continuum – any value valid between range e.g. weight, height
-
Discrete: data can only take certain values – usually integers,
often counts e.g. number of children in a family
What is categorical data?
Individuals fall into one of a number of separate categories, Can be 2, 3 or more categories:
what kind of data is made up of 2 categories
2 categories: dichotomous or binary data
what is the difference between ordered and unordered?
Ordered data has a specific sequence or arrangement, like a list of numbers sorted from smallest to largest. Unordered data doesn’t have a defined sequence, like a set of items in a bag without any particular order.
What is a box plot used to show?
Box plot for continuous data
- median = horizontal line in box
- upper quartile = top edge of the box
- lower quartile = lower edge of box
- Whisker length up to 1.5 times width of box
- Outliers shown as dots
Describe shapes of distribution.
