Trend Studies

Definition ||Advantages ||Disadvantages

The trend study is probably the most common longitudinal study among others. A trend study samples different groups of people at different points in time from the same population. For example, trend studies are common around public opinion poll. Suppose that 2 months before a year-long gun control campaign, a sample of adults is drawn: 64% report that they're in favor of a strict gun control regulation and 34% report that they are not. A year later, a different sample drawn from the same population shows a change: 75% report that they're in favor of gun control and 25% report that they are not. This is a sample example of trend study. Trend studies provide information about net changes at an aggregate level. In the example we know that in the period under consideration, the gun control program gained 11% more support. However, we do not know how many people changed their positions (from con to pro OR from pro to con), nor do we know how many stayed with their original choice. To determine both the gross change and the net change, a panel study would be necessary.

Characteristics

Data is collected from the population at more than one point in time. (This does not always mean that the same subjects are used to collect data at more than one point in time, but that the subjects are selected from the population for data at more than one point in time).

There is no experimental manipulation of variables, or more specifically, the investigator has no control over the independent variable.

This kind of study involves data collection only. No intervention is made by the investigator other than his/her method or tool to collect data.

In analyzing the data, the investigator draws conclusions and may attempt to find correlations between variables. Therefore, trend studies are uniquely appropriate for assessing change over time and for situation relating (prediction) questions because variables are measured at more than one time. However, this method is deficient for situation producing questions (causal) because there in no manipulation of the independent variable.