Methods of Research, Longitudinal Research

1. LONGITUDINAL
STUDY

2. TABLE OF CONTENTS
Definition of
Longitudinal Study
01 Types of
Longitudinal Studies
02 Advantages &
Disadvantages
03
Trend Studies
04 Cohort Analysis
05 Panel Study
06
References
07

3. Longitudinal Study
• a type of correlational research in which
researchers observe and collect data on a
number of variables without trying to
influence those variables.
• in this study, researchers repeatedly
examine the same individuals to detect any
changes that might occur over a period of
time.

4. • The oldest Longitudinal Studies were launched
in the United States.
• The first study measuring the impact of
participation in preschool on the child outcomes
dates back to the High/Scope Perry Preschool
Project, which started in 1962. The sample size
of this study was only 123 children.

5. Longitudinal data are used for:
Attitude and
Image Check
Market tracking
The impact of
disease and
Treatment
Method
Brand Switching

6. Longitudinal Study:
Advantages & Disadvantages
Advantages Disadvantages
 Less variables
 Lots of data
 More trustworthy
because it is the same
participants.
 Allow researchers to
follow their subjects in
real time.
 Costly
 Time Consuming
 Attrition, which
occurs when
participants drop out
of a study.

7. Types of Longitudinal Studies:
Trend
Studies
Cohort
Analysis
Panel
Study

8. Trend Studies:
• most common type of Longitudinal Study in
mass media research.
• samples different groups of people at different
times from the same population.
• common around presidential election time.

9. Trend Studies: Examples
• In the United States, a question about satisfaction with the President's
performance has been asked hundred of times
• *Public Opinion Quarterly has a regular section entitled "The Polls"
that allows researchers to construct trend data on selected topics. The
following trend data have appeared:
- A 16 year sampling of attitude about the Soviet Union.
- A 15 year trend about attitude towards environmental issues.
- A 5 year compilation of Israeli attitude towards security.
*Public Opinion Quarterly is an academic journal published by Oxford
University Press for the American Association for Public Opinion Research.

10. Trend Studies: Advantages
• These help to investigate a sample from a
general population over time with respect to
some phenomenon.
• This studies permit researchers to examine
pattern & rate of changes & to make prediction
about future direction based on previously
identified patterns & rates of changes.

11. Cohort Analysis:
• A cohort is any group of individuals who are
linked in some way or who have experienced the
same significant life event within a given period.
• Any study in which some characteristic of one or
more cohorts is measured at two or more points in
time.
• widely used in advertising and marketing research
and studies of public opinion. .

12. Cohort Analysis: Examples
• Rentz et al (1983) conducted a cohort
analysis of consumers born in four time
periods 1931- 1940, 1941-1950, 1951-1960,
1961-1970. Soft drink consumption was the
dependent variable.
• Rosengren and Windahl (1989) used cohort
analysis as part of their in-depth
longitudinal study of T.V. usage by
Swedish youngsters.

13. Cohort Studies: Advantages
• The best way to ascertain both the incidence and
natural history of a disorder.
• Useful in investigation of multiple outcomes that
might arise after a single exposure.
• Also useful in the study of rare exposures.
• Reduce the risk of survivor bias
• Allow calculation of incidence rates, relative risks,
and confidence intervals.

14. Panel Studies:
• measure the same sample of respondents at different
points in time.
• Unlike Trend Studies, panel studies can reveal
information about both net change and gross change in
the dependent variable.
• Mostly used in market research, (e.g. advertising effect,
product improvements, brand comparisons)

15. Kinds of Panel Studies:
• Static panels- same member throughout
• Dynamic panels- members substituted
• from time to time

16. Panel Studies: Example
• The collection of national television audience
data by the A.C. Nielsen Company. Neilsen's
sample contains of approximately 4,000
households located across the United States.

17. Panel Studies: Advantages
• Panels gain expertise and can give good data
• Could establish cause-effect relationship
• Rapport between researcher and panel members
established.

18. REFERENCES:
• Scribbr : https://www.scribbr.com/methodology/longitudinal-
study/#:~:text=In%20a%20longitudinal%20study%2C%20resea
rchers,trying%20to%20influence%20those%20variables.
• Slideshare:
https://www.slideshare.net/nadianaseem5/longitudinal-research
• http://whiz-masscommunication.blogspot.com/2011/08/cohort-
analysis-trend-studies-and-panel.html