What are three types of Longitudinal designs?

Question

What will be an ideal response?

Answer 1

1) Repeated Cross-Sectional Designs
Studies that use a repeated cross-sectional design, also known as a trend study, have become fixtures of the political arena around election time. Particularly in presidential election years, we accustom ourselves to reading weekly, even daily, reports on the percentage of the population that supports each candidate. Similar polls are conducted to track sentiment on many other social issues. For example, a 1993 poll reported that 52% of adult Americans supported a ban on the possession of handguns compared with 41% in a similar poll conducted in 1991. According to pollster Louis Harris, this increase indicated a “sea change” in public attitudes (cited in Barringer, 1993, p. A14). Another researcher said, “It shows that people are responding to their experience [of an increase in handgun-related killings]” (cited in Barringer, 1993, p. A14).
Repeated cross-sectional surveys are conducted as follows:
1. A sample is drawn from a population at Time 1, and data are collected from the sample.
2. As time passes, some people leave the population and others enter it.
3. At Time 2, a different sample is drawn from this population.
Repeated cross-sectional design (trend study) -- A type of longitudinal study in which data are collected at two or more points in time from different samples of the same population; also known as a trend study
2) Fixed-Sample Panel Designs
Panel designs allow us to identify changes in individuals, groups, or whatever we are studying. This is the process for conducting fixed-sample panel designs:
1. A sample (called a panel) is drawn from a population at Time 1, and data are collected from the sample.
2. As time passes, some panel members become unavailable for follow-up, and the population changes.
3. At Time 2, data are collected from the same people as at Time 1 (the panel), except for those people who cannot be located.
Fixed-sample panel design (panel study) A type of longitudinal study in which data are collected from the same individuals—the panel—at two or more points in time. In another type of panel design, panel members who leave are replaced with new members.
Because a panel design follows the same individuals, it is better than a repeated cross-sectional design for testing causal hypotheses. For example, Sampson and Laub (1990) used a fixed-sample panel design to investigate the effect of childhood deviance on adult crime. They studied a sample of white males in Boston when the subjects were between 10 and 17 years old and then followed up when the subjects were in their adult years. Data were collected from multiple sources, including the subjects themselves and criminal justice records. The researchers found that children who had been committed to a correctional school for persistent delinquency were much more likely than other children in the study to commit crimes as adults: 61% were arrested between the ages of 25 and 32, compared with 14% of those who had not been in correctional schools as juveniles (p. 614). In this study, juvenile delinquency unquestionably occurred before adult criminality. If the researchers had used a cross-sectional design to study the past of adults, the juvenile delinquency measure might have been biased by memory lapses, by self-serving recollections about behavior as juveniles, or by loss of agency records. The problem, of course, is that tracking people for years is extremely expensive, and many people in the original sample drop out for various reasons. Panel designs are also a challenge to implement successfully, and often are not even attempted, because of two major difficulties:
1. Expense and attrition. It can be difficult, and very expensive, to keep track of individuals over a long period, and inevitably, the proportion of panel members who can be located for follow-up will decline over time. Panel studies often lose more than one quarter of their members through attrition (Miller, 1991), and because those who are lost are often dissimilar to those who remain in the panel, the sample’s characteristics begin to change and internal validity is compromised.
2. Subject fatigue. Panel members may grow weary of repeated interviews and drop out of the study, or they may become so used to answering the standard questions in the survey that they start giving stock answers rather than actually thinking about their current feelings or actions (Campbell, 1992). This is called the problem of subject fatigue. Fortunately, subjects do not often seem to become fatigued in this way, particularly if the research staff have maintained positive relations with them.
Subject fatigue Problems caused by panel members growing weary of repeated interviews and dropping out of a study or becoming so used to answering the standard questions in the survey that they start giving stock or thoughtless answers.
3) Event-Based Designs
Event-based design (cohort study) A type of longitudinal study in which data are collected at two or more points in time from individuals in a cohort.
Cohort Individuals or groups with a common starting point. Examples of a cohort include college class of 1997, people who graduated from high school in the 1980s, General Motors employees who started work between 1990 and the year 2000, and people who were born in the late 1940s or the 1950s (the baby boom generation).
In an event-based design, often called a cohort study, the follow-up samples (at one or more times) are selected from the same cohort, people who all have experienced a similar event or a common starting point. Examples include the following:
• Birth cohorts: those who share a common period of birth (those born in the 1940s, 1950s, 1960s, etc.)
• Seniority cohorts: those who have worked at the same place for about five years, about 10 years, and so on
• School cohorts: freshmen, sophomores, juniors, and seniors