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Related Concept Videos

Longitudinal Research02:20

Longitudinal Research

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Sometimes we want to see how people change over time, as in studies of human development and lifespan. When we test the same group of individuals repeatedly over an extended period of time, we are conducting longitudinal research. Longitudinal research is a research design in which data-gathering is administered repeatedly over an extended period of time. For example, we may survey a group of individuals about their dietary habits at age 20, retest them a decade later at age 30, and then again...
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Sample Size Calculation01:19

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Knowledge of the sample size is the first requirement to conduct random sampling or an experiment. The sample size is the total number of units, observations, or groups (in some cases) used to get the data to estimate a population parameter. As the name suggests, the sample size is that of the sample drawn from the population and differs from the population size.
The sample size for the given experiment or sampling effort is fundamental to any study design. Sample size decides the number of...
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One-Way ANOVA: Equal Sample Sizes01:15

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One-Way ANOVA can be performed on three or more samples with equal or unequal sample sizes. When one-way ANOVA is performed on two datasets with samples of equal sizes, it can be easily observed that the computed F statistic is highly sensitive to the sample mean.
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One-Way ANOVA: Unequal Sample Sizes01:15

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One-way ANOVA can be performed on three or more samples of unequal sizes. However, calculations get complicated when sample sizes are not always the same. So, while performing ANOVA with unequal samples size, the following equation is used:
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Dose Size and Dosing Frequency: Determination Methods01:21

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Determining the optimal dose size and dosing frequency in pharmacotherapy is crucial for achieving therapeutic effectiveness while minimizing adverse effects. This article explores the methodologies employed in determining these parameters, focusing on their significance and interplay to tailor dosing regimens.Dose Size: Dose size refers to the amount of a drug administered in a single dose. It is determined based on the drug's pharmacodynamics and pharmacokinetics properties and...
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One-Compartment Open Model: Urinary Excretion Data and Determination of k01:11

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The one-compartment open model leverages urinary excretion data to estimate renal clearance, which gauges the kidney's capacity to expel a drug. This method offers several benefits, including directly measuring drug elimination and assessing the kidney's contribution to overall drug clearance. However, this approach has limitations. It assumes sole renal excretion of the drug, which is not true for all drugs. Accurate urinary excretion and plasma drug concentration measurement can also...
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Sample size determination for mediation analysis of longitudinal data.

Haitao Pan1, Suyu Liu2, Danmin Miao3

  • 1Department of Biostatistics, St. Jude Children's Research Hospital, Memphis, TN, 38105, USA.

BMC Medical Research Methodology
|March 28, 2018
PubMed
Summary

Determining sample size for longitudinal mediation studies is complex. Simulations show the product method and bootstrapping are more powerful than Sobel's method, with the product method recommended for practical application.

Keywords:
Longitudinal studyMediation analysisSample size determination

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Area of Science:

  • Psychometrics
  • Biostatistics
  • Longitudinal Data Analysis

Background:

  • Sample size determination is critical for the statistical power and reliability of longitudinal mediation studies.
  • Traditional methods for sample size calculation are often inadequate for complex longitudinal mediation designs.

Purpose of the Study:

  • To provide guidance on sample size planning for longitudinal mediation studies using multilevel mediation models.
  • To determine the sample size needed to achieve 80% statistical power across various mediation effect sizes and within-subject correlations.

Main Methods:

  • Utilized simulation studies to evaluate sample size requirements for three mediation testing methods: Sobel's, distribution of the product, and bootstrapping.
  • Calculated sample sizes based on achieving 80% power under different mediation effect sizes, within-subject correlations (ICC), and numbers of repeated measures.

Main Results:

  • Sobel's method required the largest sample size for 80% power.
  • The distribution of the product and bootstrapping methods were more powerful, requiring smaller sample sizes.
  • Higher within-subject correlations (ICC) generally necessitated larger sample sizes for all methods.

Conclusions:

  • The distribution of the product and bootstrapping methods demonstrate superior performance over Sobel's method for longitudinal mediation analysis.
  • The product method is recommended for practical use due to its efficiency and comparable power to bootstrapping.
  • An R package is available to assist with sample size determination for mediation in longitudinal study designs.