What is a “Meta-analysis”?
A “meta-analysis” is a statistical technique used by psychologists. in a number of research studies. meta-analysis gives
them a quantitative tool to analyze statistically data drawn from a number of studies, performed over a period of time. In
other words, A meta-analysis is a type of statistical technique that involves combining and analyzing the results of many
different individual studies devoted to a specific topic.
How is it “done”
Individual or teams of Meta-analysis researchers combines the results of several studies performed over a period of time.
Only studies that address similar aims/hypotheses should be chosen. Because the IV’s in these studies tend to be
measured in different ways, meta-analysis researchers focus statistically studying the “effect size” of the DV in the
various research studies as a way to assess overall trends of the different research studi es. By focusing on effect size,
they allow for comparisons to be made between different research studies (in the same way that turning raw data into
percentages allows us to compare very different sets of numbers).
Note that “effect size” is something we use in our everyday lives. For instance, we might evaluate a weight loss program
boast that it leads to an average weight loss of 30 pounds. This is the “size of the effect” or effect size of the average
person who engages in the program. It is a very useful comparison tool.
Why is it done?
Psychologists and medical researchers increasingly use this method, as a way of avoiding time-consuming and intricate
studies, largely repeating the work of previous research. Furthermore, social studies often use very small sample sizes, so
any statistics used generally give results containing large margins of error. This can be a major problem when interpreting
and drawing conclusions, because it can mask any underlying trends or correlations. Such conclusions are only tenuous, at
best, and leave the research open for criticism. Therefore, the process of Meta-analysis is used because it draws from a
larger body of research, and using powerful statistical analysis on the large groups of related data. This gives a much larger
sample population and is more likely to generate meaningful and usable data.
Said another way, Meta-analysis is conducted because it allows researchers to get a better look at overall trends and identify
possible relationships that might exist. Since a meta-analysis combines many smaller samples into a much larger pool of data,
researchers can sometimes identify trends that could not be seen in smaller-scale studies. A meta-analysis can be
particularly useful if a number of factors have been associated with a particular phenomenon, and can often be used to
narrow in on the most important contributing factors. This technique can also be used when a number of smaller studies
have found contradictory or weak results.
The Advantages of Meta-Analysis
 Meta-analysis is an excellent way of reducing the complexity and breadth of research, allowing funds to be diverted
elsewhere. For rare medical conditions, it allows researchers to collect data from further afield than would be possible
for one research group.
 As the method becomes more common, database programs have made the process much easier, with professionals
working in parallel able to enter their results and access the data. This allows constant quality assessments and also
reducing the chances of unnecessary repeat research, as papers can often take many months to be published, and the
computer records ensure that any researcher is aware of the latest directions and results.
 The field of meta study is also a lot more rigorous than the traditional literature review, which often relies heavily upon
the individual interpretation of the researcher.
 When used with the databases, a meta study allows a much wider net to be cast than by the traditional literature
review, and is excellent for highlighting correlations and links between studies that may not be readily apparent as well
as ensuring that the compiler does not subconsciously infer correlations that do not exist.
The Disadvantages of Meta-Analysis
 There are a number of disadvantages to meta-analysis, of which a researcher must be aware before relying upon the
data and generated statistics.
 The main problem is that there is the potential for publication bias and skewed data.
 Research generating results not refuting a hypothesis may tend to remain unpublished, or risks not being entered into
the database. If the meta study is restricted to the research with positive results, then the validity is compromised.
 The researcher compiling the data must make sure that all research is quantitative, rather than qualitative, and that the
data is comparable across the various research programs, allowing a genuine statistical analysis.
 It is important to pre-select the studies, ensuring that all of the research used is of a sufficient quality to be used.
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One erroneous or poorly conducted study can place the results of the entire meta-analysis at risk. On the other hand,
setting almost unattainable criteria and criteria for inclusion can leave the meta study with too small a sample size to
be statistically relevant.
Striking a balance can be a little tricky, but the whole field is in a state of constant development, incorporating protocols
similar to the scientific method used for normal quantitative research.
Finding the data is rapidly becoming the real key, with skilled meta-analysts developing a skill-set of library based skills,
finding information buried in government reports and conference data, developing the knack of assessing the quality of
sources quickly and effectively.
Article to read:
Meta-Analysis Helps Psychologists Build Knowledge
When scientists want to know the answer to a question that’s been studied a great deal, they conduct something
called a meta-analysis, pooling data from multiple studies to arrive at one combined answer. Some people think
this creates a chilling effect, shutting off further inquiry. But the authors of a new paper published inPerspectives
in Psychological Science, a journal of the Association for Psychological Science, write that meta-analysis
actually helps scientific fields develop.
There are many meta-analyses in psychology and medicine, areas where studies find often conflicting results. For
example, some experiments might find that a particular drug decreases the risk of heart attack, while other
experiments might find the drug doesn’t have any particular effect. A meta-analysis takes the results from all
published studies on the same question and combines them; it’s as if someone had done a single study with a
much larger sample size.
The answers that a meta-analysis comes up with can guide the field. But it may also stop scientists from looking at
questions related to whatever the meta-analysis was about. “We started out asking the question, does it have a
chilling effect? What happens after a meta-analysis?” says Richard D. Arvey of the National University of
Singapore, who co-wrote the article with graduate student Meow Lan Evelyn Chan. They looked at a particular area
and found that researchers did continue to conduct studies after the meta-analysis was published.
Meta-analysis can be very useful, Arvey and Chan argue. Arvey gives an example from his own experience: He
was an expert witness in an age discrimination case. The workers who thought they had been discriminated
against had an expert witness who presented a study that found the kinds of things the company was accused of
were because of age discrimination. But Arvey used a meta-analysis to show, he says, that “The data this person
had produced was an outlier, a very unusual result compared to all the other studies.” He showed that this study
did not represent what had been found by the field as a whole.
This method can also help guide scientists on what kinds of work to subsequently explore. Arvey is starting to study
the neurological basis of leadership, and he’s using meta-analysis to find out what personality characteristics are
generally associated with leadership. “I will start looking at specific measures of those traits in my own research,”
he says.
Just the fact that it’s possible to do meta-analyses in psychology shows that psychology is a fairly mature field,
Arvey says. “In order to do meta-analysis, you have to have enough scholars who have studied the phenomenon in
the first place.” Meta-analysis has helped psychology mature over the last 20 years, he says, helping scientists to
develop paradigms for understanding human behavior and focus more on important questions.
January 6, 2012