Statistics - study design Flashcards
RCT definition
Participants randomly allocated to intervention or control group (e.g. standard treatment or placebo)
e.g. Testing drug efficacy
Practical/ethical problems may limit use
Cohort study definition + outcome measure + example
Observational and prospective. Two (or more) are selected according to their exposure to a particular agent (e.g. medicine, toxin) and followed up to see how many develop a disease or other outcome.
Outcome measure: relative risk
e.g. Framingham heart study
Case-control study definition + outcome measure + example
Observational and retrospective. Patients with a particular condition (cases) are identified and matched with controls.Data is then collected on past exposure to a possible causal agent for the condition.
Outcome measure: Odds ratio
e.g. e.g. living near electric pylons is a RF for childhood leukaemia
Inexpensive, produce quick results
Useful for studying rare conditions
Prone to confounding
Cross sectional survey
Provide a ‘snapshot’, sometimes called prevalence studies
Provide weak evidence of cause and effect
Students t-test (Paired data)
refers to data obtained from a single group of patients, e.g. Measurement before and after an intervention.
Students T-test (Unpaired data)
Unpaired data comes from two different groups of patients, e.g. Comparing response to different interventions in two groups
Mann-whitney U test
- compares ordinal, interval, or ratio scales of unpaired data
Wilcoxon signed-rank test
compares two sets of observations on a single sample, e.g. a ‘before’ and ‘after’ test on the same population following an intervention
Chi-squared test
used to compare proportions or percentages e.g. compares the percentage of patients who improved following two different interventions
Spearmans coefficient
Correlation between non parametric (non normally distributed) data
Pearson coefficient
Correlation between parametric (normally distributed) data
Phase one
small studies (e.g. 100) on healthy volunteers
used to assess pharmacodynamics and pharmacokinetics
Phase two
- small studies (e.g. 100-300) on actual patients
- examines efficacy, adverse effects
Phase three
- larger studies (e.g. 500-5,000 patients)
- examines efficacy, adverse effects
- may compare drug with existing treatments
- studies of special groups e.g. renal, elderly
Phase four
post-marketing surveillance
Thematic analysis
a method of qualitative data analysis. Qualitative studies seek to explore experiences and generate hypotheses,
Systematic review
attempts to identify, appraise and synthesise all the empirical evidence that meets pre-specified eligibility criteria to answer a specific research question.
Meta-analysis
Meta-analysis involves statistically combining the results of multiple studies to produce an overall effect estimate
Variable
is any characteristics, number, or quantity that can be measured or counted.
E,g age, sex, business income and expenses, country of birth, capital expenditure, eye colour and vehicle trpe
Independent variable
is something that the experimenter purposely changes over the course of the investigation.
Dependent variable
The dependent variable is the one that is observed and changes in response to the independent variable.
Linear regression
When analyzing data on a scatter plot, linear regression may be used to predict how much one variable changes when a second variable is changed
Funnel plot
Used to demonstrate the existence of publication bias in meta-analyses
Histogram
A graphical display of continuous data where the values have been categorised into a number of categories
Forest plot
Forest plots are usually found in meta-analyses and provide a graphical representation of the strength of evidence of the constituent trials
Scatter plot
Graphical representation using Cartesian coordinates to display values for two variables for a set of data
Kaplan-Meier survival plot
A plot of the Kaplan-Meier estimate of the survival function showing decreasing survival with time
ANOVA
Is a statistical test to demonstrate statistically significant differences between the means of several groups. It is similar to a student’s t-test apart from that ANOVA allows the comparison of more than just two means.
