Quantitative Research Designs

Research designs for PICO

• RCT

• Cohort analytic study

• Single group pre/post-test design

• Case-control study

Research designs for PECO

• cohort study

• case control study

• cross sectional study

RCT

• Random assignment of participants (random allocation)

• There can be continous outcomes or discrete outcome

Continous outcome RCT

Numerical variable where measurements can take any value along a continuum

Discrete outcome RCT

Refers to when there is only two possible values like outcome vs no outcome

Strengths of RCT

• Random allocation

• Temporality where exposure precedes outcome

Weaknesses of RCT

• Costly

• Time is required for follow up

• Patients that agree to participate may differ from target population (generalizability)

• Not always ethical or feasible

Cohort analytic study

• Compares an expiremental and controul group when random allocation is not feasible or ethical

Strengths of cohort analytic study

• Potentially less costly and more feasible than an RCT

• Exposure precedes outcome - temporality

Weaknesses of cohort analytic study

• costly

• selection bias where groups may differ in ways other than exposure to the intervention

• baseline differences where groups may differ in characteristics before intervention began

single group pre/post-test design

• used when it is not possble to have a comparison or control group (experiemental and control group are the same)

• outcomes are measured prior to and after an intervention

case control study

• compares people who have a specific outcome or disease with people do not have outcome to look retrospectively at past exposures

• can determine if the exposure is associated or correlated with the outcome but cannot confirm that the intervention causes the outcome

two group, post-test only design

• measures outcome data (post-test) in participants following exposure to the intervention

cohort study

• follows a sample forwards in time (prospectively) or backwards in time (retrospectively) to see if they are exposed to the exposure of interest and if they develop the outcome of interest

• no random allocation

strengths of cohort study

• good for studying rare exposures

• temporality

• multiple outcomes

• best for evaluating risk factors

weaknesses of cohort study

• lack of a control group

• inefficient for studying rare outcomes

• follow up takes a long time

  • contamination where long follow ups could mean that other factors could cause certain outcomes

case-control study

• identifies participants with AND without outcome of interest and looks retrospectively to collect data about participant exposure to a certain risk factor

strengths of case-control study

• quicker and more cost-efficient than cohort study

• good for study of rare OUTCOMES and common EXPOSURES

• includes control group

• can examine multiple exposures

weaknesses of case control study

• difficult to obtain temporality

• difficult to obtain accurate information on exposure

• cannot examine multiple outcomes

cross sectional study

• follows participants throughout life at the same point in time for each participant

• measures exposure and outcome data

descriptive cross sectional survey

• group of people interviewed/asked to complete a survey to determine whether they have experienced an exposure of interest and an outcome of interest

strengths of descriptive cross sectional survey

• cost efficient and quick

• good for exploratory research phase where potential causal factors can be identified

weaknesses of descriptive cross sectional survey

• no temporality

• difficult to obtain exposure information

• there may be no control group