Meta Analysis

A meta-analysis is similar to a smoothie in that you combine many ingredients, and you get a single drink at the end. A meta-analysis is a quantitative technique that combines the results of multiple studies and ends with a summative figure/ estimate. A meta-analysis essentially is a summary, in effect, of numerous studies to form one finding that covers the area of study.  

Meta Analysis Meta Analysis

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Table of contents

    The purpose of meta-analyses is to identify if the collaborative study’s findings support or disprove a hypothesis proposed by the research overall.

    • We will start by looking at the meta-analysis meaning and how a meta-analysis in research is used.
    • Moving on to cover the meta-analysis methodology frequently used by researchers.
    • Then we will take a look at an actual meta-analysis example.
    • Afterwards, we will explore meta-analysis vs systematic review to identify the stark differences between the two research methods.
    • Finally, we will look at the advantages and disadvantages of using meta-analysis in psychology research.

    Meta Analysis, research diagram, StudySmarterFigure 1: Research. Credit: flaticon.com/Freepik

    The Meta-Analysis Meaning

    What do we mean by a meta-analysis?

    A meta-analysis is a research technique researchers frequently use in psychology to summarise key findings of multiple studies. The research method collects quantitative, meaning numerical data.

    A meta-analysis is a quantitative, systematic method that summarises the findings of multiple studies investigating similar phenomena.

    Meta-Analysis in Research

    Researchers use a meta-analysis to understand psychology research’s general direction in a specific area.

    For instance, if a researcher wants to see if an overwhelming amount of research supports or disproves a theory.

    The research method is also commonly used to identify whether current research supports and establishes existing interventions as effective or ineffective. Or to find a more precise, generalisable conclusion. As meta-analyses utilise multiple studies to form a conclusion, the findings are more likely to be statistically significant as a larger data pool is used.

    Meta-Analysis Methodology

    When deciding to perform a meta-analysis of existing research, a researcher will typically involve in the following steps:

    • Researchers identify the area of interest for the research and formulate a hypothesis.
    • Researchers create inclusion/exclusion criteria. For example, in a meta-analysis looking into the effects of exercise on mood, exclusion criteria may include studies using participants that are using medication that affects affective states.

    The inclusion criteria refer to characteristics that the researcher wishes to investigate. And the exclusion criteria should point out the features the researcher does not want to explore.

    • Researchers will use a database to identify all of the research similar to what the hypothesis is investigating. Several established databases in psychology include published work. In this stage, researchers need to search key terms that summarise what the meta-analysis is investigating to identify studies that also investigated similar factors/ hypotheses.
    • Researchers will determine which studies will be used based on the inclusion/exclusion criteria. From the studies found in the database, the researcher must decide whether they will be used.
      • Studies included meeting the criteria of the inclusion criterion.
      • Studies excluded meeting the criteria of the exclusion criterion.
    • Researchers appraise the research studies. Appraising studies is a crucial stage in the meta-analysis methodology that checks the reliability and validity of included studies. Studies low in reliability or validity are usually not included in the meta-analysis.

    Studies that are low in reliability/validity will also lower the reliability/validity of the meta-analysis findings.

    • Once they have compiled the information and statistically analysed the results, they can form a conclusion of whether the analysis supports/disproves the hypothesis initially proposed.

    Meta-Analysis Example

    Van Ijzendoorn and Kroonenberg (1988) performed a meta-analysis to identify cross-cultural and intra-cultural differences between attachment styles.

    The meta-analysis reviewed a total of 32 studies from eight different countries. The inclusion criteria of the meta-analysis were studies that used:

    1. The strange situation was used to identify attachment styles.

    2. The studies investigated mother-infant attachment styles.

    3. The studies used the same attachment classification system as in Ainsworth’s Strange Situation – type A (insecure avoidant), type B (secure), and type C (insecure avoidant).

    Studies not meeting these requirements were excluded from the analysis. Further exclusion criteria included: studies that recruited participants with developmental disorders.

    For the analysis of the study, the researchers calculated each country’s average percentage and mean score of attachment styles.

    The results of the meta-analysis were the following:

    • Secure attachments were the most common attachment style in each country analysed.

    • Western countries had a higher mean score of insecure-avoidant attachments than Eastern countries.

    • Eastern countries had a higher mean score of insecure-ambivalent attachments than Western countries.

    This meta-analysis example showed the importance of meta-analysis in research as it allowed the researchers to compare the data from multiple countries relatively quickly and cheaply. And it would have been too difficult for the researchers to independently collect primary data from each of the eight countries due to time, cost and language barriers.

    Meta-Analysis vs Systematic Review

    Meta-analysis and systematic review are standard research techniques used in psychology. Although similar research processes, stark differences between the two exist.

    A systematic review is one of the stages of the meta-analysis methodology. During a systematic review, the researcher uses a precise method to collect relevant studies from scientific databases relevant to the research area. Like a meta-analysis, the researcher creates and uses inclusion/ exclusion criteria. Rather than giving a quantitative summative figure, it identifies and summarises all the relevant research concerning the research question.

    Advantages and Disadvantages of Meta-Analysis

    Let’s discuss the advantages and disadvantages of meta-analysis in psychology research.

    AdvantagesDisadvantages
    • It allows researchers to analyse data from a large sample. The results from the meta-analysis are more likely to be generalisable.
    • This method is relatively cheap, as the studies have already been conducted, and the results are already available.
    • Meta-analyses draw conclusions based on evidence from multiple empirical sources. Therefore, there is an increased likelihood that meta-analysis findings will be more valid than independent experimental research that forms a conclusion based on a single study’s findings.
    • Meta-analysis in research has many practical applications in psychology. For example, it can provide a reliable, precise summary of whether an intervention is effective as a treatment method.
    • Researchers need to ensure the research studies they are combining into their meta-analysis are reliable and valid, as this can affect the reliability and validity of the meta-analysis.
    • The studies included in the meta-analysis will likely use different research designs, raising the question of whether the data is comparable.
    • Although the researcher does not collect the data, the meta-analysis methodology can still be time-consuming. It will take time for researchers to identify all of the relevant research. In addition, they will need to determine if the studies are of acceptable standards regarding reliability and validity.
    • Suppose the researcher is investigating a new area of research or a phenomenon many researchers have not investigated before. In that case, it may not be appropriate to use a meta-analysis.
    • Esterhuizen and Thabane (2016) emphasised that meta-analyses are often criticised for including poor-quality research, comparing heterogeneous research and not addressing publication bias.
    • The criterion used may not be appropriate for the hypothesis and may incorrectly exclude or include studies in the meta-analysis, affecting the results. Thus, carefully considering what to include or exclude needs to be done, and it is not always perfect.

    Meta Analysis - Key Takeaways

    • A meta-analysis is a quantitative, systematic method that summarises the findings of multiple studies investigating similar phenomena.
    • A meta-analysis example is Van Ijzendoorn and Kroonenberg (1988). The research aimed to identify cross-cultural and intra-cultural differences between attachment styles.
    • A meta-analysis in research has many uses, such as identifying the general direction of research or identifying if findings suggest interventions are effective or ineffective.
    • There are many advantages, such as its cost-effectiveness and practicality to the research method. But it does not come without disadvantages, like it can be time-consuming or whether the meta-analysis will find quality results, i.e. reliable or valid.

    Frequently Asked Questions about Meta Analysis

    What is a meta-analysis?

    A meta-analysis is a quantitative, systematic method that summarises the findings of multiple studies that are investigating similar phenomena. 

    How to do a meta-analysis?

    There are several stages of the meta-analysis methodology. These are:

    1. Identifying a research question and forming a hypothesis 
    2. Creating an inclusion/exclusion criterion for studies that will be included/excluded from the meta-analysis
    3. Systematic review
    4. Appraise the relevant research 
    5. Carry out the analysis 
    6. Form a conclusion of whether the data supports/disproves the hypothesis.

    What is a meta-analysis in research?

    Using a meta-analysis in research is useful when: 

    • Trying to understand the general direction of psychology’s existing research, for instance, if an overwhelming amount of research supports or disproves a theory. 
    • Or, to identify if existing research establishes existing interventions as effective or ineffective
    • Finding a more precise, generalisable conclusion.

    What is systematic review vs meta-analysis?

    A systematic review is one of the stages of the meta-analysis methodology. During a systematic review, the researcher uses a precise method to collect relevant studies from scientific databases relevant to the research area. Like a meta-analysis, the researcher creates and uses inclusion/ exclusion criteria. Rather than giving a quantitative summative figure, it identifies and summarises all the relevant research concerning the research question.

    What is a meta-analysis with an example?

    Van Ijzendoorn and Kroonenberg (1988) conducted a meta-analysis to identify cross-cultural and intra-cultural differences between attachment styles. Thus, a meta-analysis is a research method used to summarise the findings of multiple studies investigating a similar research topic. 

    Test your knowledge with multiple choice flashcards

    Which of the following studies used a meta-analysis?

    Which of the following steps are aspects of meta-analysis and systematic reviews? 

    Should research used in meta-analyses be heterogeneous? 

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