Growth is quantitative change in an organism over time. It may be positive or negative point study usually focus on height, weight, organ growth, bones, muscles etc
Longitudinal method.
Repeated measurement of same individual or groups at different times. For example height change with age. This provides a pattern of growth of height in children of a group
Can be plotted on a graph.
Provides us insight on factors affecting the treat like height affected by nutrition, war, socio-economic condition, region and so on.
Distance curve shows overall growth which time.
Velocity curve is rate of growth per unit time. It indicates how quickly growth is taking place.
Advantages.
accurate growth pattern of individuals.
Allows us to study speed of growth.
Interlinked. CanCan study various traits like secondary sexual traits and dentition.
Accurate study of factors affecting growth
Limits.
time consuming and. Time as a confounding variable
not cost-effective.
Not easy to obtain large sample and subjects mein stop coming.
Researcher gets old.
Baxter 1995 longitudinal study on athletic males swimmers Soccer and tennis players. About 10 years.
Cross sectional method
Studies different individuals at various stages of life. For example studying children between 6 and 16 so the researcher will take a sample from each age group and compare them.
Advantage.
Fast
cost effective and
Less burden on researcher.
Fair estimate on data
Limitation. not accurate and cannot precisely point towards factors affecting growth specially in an individual. persons as confounding variable.
Luna 1983. Cross sectional study of effect of puberty on insulin.