Question

1. . Use practical examples to distinguish between a cross-sectional survey and a

longitudinal survey.

Answer 1

Cross sectional survey

It is an observational study where researchers record information about their subjects without manipulationg the study environment.They are one point in time observations uses different samples for their studies.It gives the snapshot of a given point in time,change at a societal level.some examples include british social attitudes survey,labour force survey etc..

Let us take a practical example for the study.Here we would simply measure the cholesterol level of daily walkers and non walkers in the same age groups.We would not influence non walkers to take up that activity,or advice daily walkers to modify their behavior.Here we might choose to measure cholesterol levels in daily walkers across two age groups,over 40 and under 40,and compare these to cholesterol levels among non walkers in the same groups.We might even create subgroups for gender.however,we would not consider past or future cholesterol levels,for these would fall outside the frame.We would look only at cholesterol levels at one point time.Advantage of a cross sectional study design is that it allows to control many different variables at the same time.For example ,look at age ,gender,income,and educational level in relation to walking and cholesterol levels.But cross sectional studies may not provide defnite information about cause and effect relationships.Therefore ,we cant know for sure daily walkers had low cholesterol levels before taking up their exercise regimes,or the behavior of daily walking helped to reduce cholesterol levels that previously very high.

Longitudinal survey

Longitudinal studies from one-off ,and they follow the same sample of people over time.They are several points in time observations.They uses the same sample and change at the individual .examples include British birth cohort studies,understanding society.Researchers do not interfere with their subjects.The benefit of a longitudinal study is that researchers are able to detect developments or changes in the characteristics of the target population at both the group and the individual level.They can establish sequences of events.As an example ,here we might choose to look at the change in cholesterol levels among women over 40 who walk daily for a period of 20 years.The study would account for the cholesterol levels at the onset of a walking regime and as the walking behavior continued over time.That is why a longitudial study is more appropriate to suggest cause and effect relationships than a cross sectional study.

Cross sectional studies can be done more quickly than longitudinal studies.Its because researchers always start a work with cross sectional study to first establish whether there are links or associations between certain variables.They would set up a longitudinal study to study cause and effect.