09/05- Longitudinal vs Cross sectional

Cross-sectional research

Definition: A research design that studies 2 or more groups at one point in time.

Advantage of Cross-sectional research

Cost-effective and quick; widely used.

Weakness of Cross-sectional research

Difficult to determine if group differences are truly developmental or due to cohort/group differences.

Example of Cross-sectional research

Comparing 5-year-olds, 7-year-olds, and 9-year-olds in one year.

Longitudinal research

Definition: A research design that follows the same participants over time.

Strength of Longitudinal research

Better for studying change over time.

Weaknesses of Longitudinal research

Time-consuming, resource-intensive, hard to modify once started, attrition, selective dropout, practice/test effects.

Example of Longitudinal research

Testing the same participants at ages 8, 12, and 18.

What is a cohort?

A cohort is a group of individuals who share a common characteristic or experience during a specific time period.

Cohort effect

Differences that are attributed to the cohort rather than age.

Why are cohort effects important in cross-sectional comparisons?

They highlight that age differences may result from historical experiences rather than just age.

Example of cohort effects

Differences between 80-year-olds and 40-year-olds due to historical life experiences.

Example of attrition

Loss of participants over time in a study.

Selective dropout

Non-random participant dropout that affects sample representativeness.

Example of selective dropout

Groups such as males, those with lower socioeconomic status, are more likely to drop out.

Prospective study design

A research design that follows participants forward into the future.

Retrospective study design

A research design that uses existing or past records/data.

Key difference between prospective and retrospective designs

Prospective looks forward, while retrospective looks back at existing records.

Correlation vs causation

Correlation does not imply causation.

Positive correlation example

Ice cream sales and shark attacks show a positive correlation.

Definition of cross-lagged correlations

Testing whether Variable X at Time 1 predicts Variable Y at Time 2.

Example of cross-lagged correlation

Examining the relationship between social media use and psychological distress.

Attrition versus selective dropout

Attrition is the general loss of participants; selective dropout refers to non-random dropout.

Practice effects

Improvement on tests due to repeated exposure, a problem mainly in longitudinal research.

Accelerated longitudinal design

Combines elements of cross-sectional and longitudinal studies, studying multiple cohorts over a shorter time.

Strength of accelerated longitudinal designs

Quicker and less resource-intensive than full longitudinal studies.

Trap: Cross-sectional does not follow the same people over time

This design compares different groups at one point in time.

Trap: Longitudinal does not necessarily prove causation

Longitudinal research identifies changes over time but does not prove causality.

Trap: Cross-sectional age differences may be cohort effects

Differences between age groups may arise from different historical contexts.

Trap: Practice effects are not real development

Improvements on repeated tests reflect familiarity, not genuine development.

Trap: Cross-lagged correlations suggest direction but do not prove causation

They can indicate temporal direction but are still correlational.

Trap: Attrition can make a longitudinal sample less representative

Loss of participants may skew the sample demographics.

Trap: Accelerated longitudinal designs are not purely longitudinal

These designs retain cross-sectional elements.

MCQ Trap: Prospective means forward-looking; retrospective means looking back

Differentiate based on temporal direction.

Key comparison: Cross-sectional vs longitudinal

Cross-sectional compares different groups at one time; longitudinal follows the same group over time.

Key comparison: Cohort effect vs practice effect

Cohort effects are related to age groups’ historical contexts; practice effects are improvements due to familiarity with tests.

Key comparison: Attrition vs selective dropout

Attrition is the general loss of participants; selective dropout is biased loss.

Key comparison: Selective dropout vs selective survival

Selective dropout refers to non-random participant loss; selective survival relates to which participants remain.

Key comparison: Prospective vs retrospective

Prospective follows participants into the future; retrospective uses past data.

Key comparison: Correlation vs causation

Correlation shows relationships between variables; causation indicates direct influence.

Key comparison: Cross-lagged correlation vs experiment

Cross-lagged correlations explore relationships over time; experiments determine causal effects.

Key comparison: Longitudinal vs accelerated longitudinal

Longitudinal studies follow individuals over time; accelerated longitudinal combines elements of both with multiple cohorts.