Statistics - study design

Question 1

RCT definition

Answer 1

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

Question 2

Cohort study definition + outcome measure + example

Answer 2

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

Question 3

Case-control study definition + outcome measure + example

Answer 3

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

Question 4

Cross sectional survey

Answer 4

Provide a ‘snapshot’, sometimes called prevalence studies
Provide weak evidence of cause and effect

Question 5

Students t-test (Paired data)

Answer 5

refers to data obtained from a single group of patients, e.g. Measurement before and after an intervention.

Question 6

Students T-test (Unpaired data)

Answer 6

Unpaired data comes from two different groups of patients, e.g. Comparing response to different interventions in two groups

Question 7

Mann-whitney U test

Answer 7

• compares ordinal, interval, or ratio scales of unpaired data

Question 8

Wilcoxon signed-rank test

Answer 8

compares two sets of observations on a single sample, e.g. a ‘before’ and ‘after’ test on the same population following an intervention

Question 9

Chi-squared test

Answer 9

used to compare proportions or percentages e.g. compares the percentage of patients who improved following two different interventions

Question 10

Spearmans coefficient

Answer 10

Correlation between non parametric (non normally distributed) data

Question 11

Pearson coefficient

Answer 11

Correlation between parametric (normally distributed) data

Question 12

Phase one

Answer 12

 small studies (e.g. 100) on healthy volunteers
 used to assess pharmacodynamics and pharmacokinetics

Question 13

Phase two

Answer 13

• small studies (e.g. 100-300) on actual patients
• examines efficacy, adverse effects

Question 14

Phase three

Answer 14

• 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

Question 15

Phase four

Answer 15

post-marketing surveillance

Question 16

Thematic analysis

Answer 16

a method of qualitative data analysis. Qualitative studies seek to explore experiences and generate hypotheses,

Question 17

Systematic review

Answer 17

attempts to identify, appraise and synthesise all the empirical evidence that meets pre-specified eligibility criteria to answer a specific research question.

Question 18

Meta-analysis

Answer 18

Meta-analysis involves statistically combining the results of multiple studies to produce an overall effect estimate

Question 19

Variable

Answer 19

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

Question 20

Independent variable

Answer 20

is something that the experimenter purposely changes over the course of the investigation.

Question 21

Dependent variable

Answer 21

The dependent variable is the one that is observed and changes in response to the independent variable.

Question 22

Linear regression

Answer 22

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

Question 23

Funnel plot

Answer 23

Used to demonstrate the existence of publication bias in meta-analyses

Question 24

Histogram

Answer 24

A graphical display of continuous data where the values have been categorised into a number of categories

Question 25

Forest plot

Answer 25

Forest plots are usually found in meta-analyses and provide a graphical representation of the strength of evidence of the constituent trials

Question 26

Scatter plot

Answer 26

Graphical representation using Cartesian coordinates to display values for two variables for a set of data

Question 27

Kaplan-Meier survival plot

Answer 27

A plot of the Kaplan-Meier estimate of the survival function showing decreasing survival with time

Question 28

ANOVA

Answer 28

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.