Ilimiy is tiykarlari

Trend studies

Trend analysis enables us to find out what has happened in the past, what is happening now and what is likely to happen in the future in a population group.

Trend studies are useful in making forecasting by extrapolating present and past trends thus making a valuable contribution to planning. Trends regarding the phenomenon under study can be correlated with other characteristics of the study population. For example, we may want to examine the changes in political preference of a study population in relation to age, gender, income or ethnicity.
Cohort studies

They are based upon the existence of a common characteristic such as year of birth, graduation or marriage, within a subgroup of a population. For example, we want to study the employment pattern of a batch of accountants who graduated from a university in 1975. To study the accountants’ career paths we would contact all the accountants who graduated from the university in 1975 to find out their employment histories. These studies could be carried out either as cross-sectional or longitudinal designs.