Selecting study design

Question 1

Why is randomisation important?

Answer 1

Key component of a robust statistical analysis how ever isn’t always completely possible

Question 2

What are different types of bias?

Answer 2

Selection, Recall, Measurement, Survivorship, Responder ect

Question 3

What is measurement bias?

Answer 3

Measuring something else and using it as an indicator of the thing we are interested in but cannot measure (proxy measures)

Question 4

What is recall bias?

Answer 4

People recalling the past incorrectly eg breast cancer diet example

Question 5

What is survivorship bias?

Answer 5

The sample only being those that have survived an ordeal eg the plane armour example

Question 6

What is confounding?

Answer 6

When an observed relationship between two variables is caused by a joint relationship with a 3rd (confounding) variable

Question 7

How can confounding’s impact be limited?

Answer 7

Random sampling

Matched sampling

Stratified sampling

Restricted sampling (eg one age group)

Question 8

What is matched sampling?

Answer 8

In a case-control test pick one in each group that is effected by the confounding eg same age

Question 9

What is stratified sampling?

Answer 9

Sample within confounding variable groups eg age

however means you end up with strata specific effect sizes

Question 10

What is multiple regression?

Answer 10

Allows for multiple explanatory variables to modelled against response variable - lets confounders be controlled

Question 11

What are pilot studies?

Answer 11

small scale study that aims to provide preliminary data to help plan a larger study

Question 12

What is a descriptive study?

Answer 12

uses existing or easy to gather data - useful for hypothesis generation but poorly controlled

Question 13

What is a correlational/observational study?

Answer 13

uses natural variation in observations to explore chosen hypothesis

Question 14

What is a manipulative study?

Answer 14

artificially manipulated a system in order to explore hypothesis

Question 15

What are studies of studies?

Answer 15

meta-analysis, systematic reviews

groups evidence to consolidate it

Question 16

What is a cross-sectional study and why is it good?

Answer 16

where a random sample is taken from a single population at a given time

response & explanatory variables are measured at the same time

(cheap & easy)

Question 17

What is a case-control study and why is it useful?

Answer 17

useful when response variable is binary (yes or no)

select individuals based on response variable and look for explanatory variables

Question 18

What is a cohort study and why is it useful?

Answer 18

Individuals are selected according to exposure variable and tracked to measure impact of response variable

Question 19

What is clinical study and why is it useful?

gold standard of medical intervention study

Answer 19

A manipulative study where individuals are recruited with pre-set criteria one group given treatment the other placebo

Randomised
Double-blind - researchers & patients don’t know what treatment is being used

Question 20

Examples of 4 different studies that can be better than large-scale randomised sampling in certain situations
(Pseudo-replication)

Answer 20

Multiple replicates from individuals

Longitudinal studies - over time

Spatial Studies - spatial patterns

Cluster-sampling - replicate within sample

Question 21

What do systematic reviews aim to do?

Answer 21

produce a quantitative or qualitative review of all the available literature relating to a hypothesis of interest

Question 22

What do Meta analyses aim to do?

Answer 22

Use statistical method to combine quantitative estimates of outcomes across multiple studies

Question 23

What do systematic reviews and meta analysis need to avoid?

Answer 23

Publication bias

hard to get replicate or negative result studies published