Transcript developmentalresearchpost

Developmental Research
Methods
Longitudinal Design
• studies the same group of individuals
(usually one age group) repeatedly over
time (usually years).
Longitudinal Design
• Example: A group of adults, ages 19-21, were
studied for 60 years to determine age changes
in mathematical ability.
Math
Test
Scores
Age at testing
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Year of testing 1930 1940 1950
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Types of Long-Term Studies
• Retrospective study – past history data
• Prospective study – longitudinal, no random
assignment
• Randomized assignment study –longitudinal
and experimental
– random assignment to the study conditions
– placebo-controlled, double-blind
– e.g. drug trials
Limitations of the Longitudinal
Research Design
• Time and cost. Study takes a long time to
complete and is usually costly.
• Selective attrition. Participants remaining at
the end of the study may differ in important
ways from those who drop out along the way.
• Repeated measurement. Effects of repeated
study and measurement are difficult to assess.
Cross-Sectional Research
• compares several groups of people who
are different in age, but similar in other
important ways at one point in time.
Cross-Sectional Research
Example: Five groups of adults were studied (say
in 2006) to determine age differences in
mathematical ability.
19-23 years old N=100
29-31 years old N=107
39-41 years old N=100
56-64 years old N=95
76-84 years old N=58
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Limitations of the Cross-Sectional
Research Design
• Cohort effects: a generational group is exposed
to the same societal influences
– confounded with age
Sequential Research Design
• combines cross-sectional and longitudinal
designs, allows checking and adjusting
for cohort effects.
Example: Three different longitudinal
studies were conducted ten years apart to
determine age and cohort differences in
mathematical ability.