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Related Concept Videos

Sample Size Calculation01:19

Sample Size Calculation

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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 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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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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Before a cell can divide, it must accurately replicate all of its chromosomes, including the DNA and its associated histone and non-histone proteins.  This process begins at numerous origins of replication during the S phase of the cell cycle in each of a cell’s chromosomes simultaneously. Certain nucleotides can act as origins of replication, but these sequences are not well defined - especially in complex, multi-cellular, eukaryotic species. The length of DNA that spans an origin...
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DNA replication involves the separation of the two strands of the double helix, with each strand serving as a template from which the new complementary strand is copied.  After replication, each double-stranded DNA includes one parental or “old” strand and one “new” strand. This is known as semiconservative replication. The resulting DNA molecules have the same sequence and are divided equally into the two daughter cells.
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Updated: Feb 4, 2026

Transferring Cognitive Tasks Between Brain Imaging Modalities: Implications for Task Design and Results Interpretation in fMRI Studies
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Transferring Cognitive Tasks Between Brain Imaging Modalities: Implications for Task Design and Results Interpretation in fMRI Studies

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Small sample sizes reduce the replicability of task-based fMRI studies.

Benjamin O Turner1, Erick J Paul2, Michael B Miller3

  • 1Wee Kim Wee School of Communication and Information, Nanyang Technological University, Singapore, 639798, Singapore.

Communications Biology
|October 2, 2018
PubMed
Summary
This summary is machine-generated.

Most functional magnetic resonance imaging (fMRI) studies lack statistical power due to small sample sizes, leading to modest replicability. Larger sample sizes are crucial for improving the reliability of fMRI research findings.

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Area of Science:

  • Neuroimaging
  • Cognitive Neuroscience
  • Psychology

Background:

  • Task-based functional magnetic resonance imaging (fMRI) studies frequently suffer from insufficient statistical power.
  • Small sample sizes are a primary contributor to underpowered neuroimaging research.
  • The continued publication of underpowered studies raises concerns about the reliability of findings in cognitive neuroscience.

Purpose of the Study:

  • To investigate the impact of sample size on the replicability of task-based fMRI results.
  • To provide accessible metrics of replicability across a range of sample sizes for fMRI researchers.
  • To advocate for the adoption of larger sample sizes in neuroimaging studies.

Main Methods:

  • Utilized large, independent samples across eleven distinct fMRI tasks.
  • Assessed replicability at multiple analytical levels relevant to fMRI researchers.
  • Evaluated the effect of varying sample sizes, from typical to substantially larger (e.g., N=100).

Main Results:

  • Replicability in fMRI studies with typical sample sizes is modest.
  • Even substantially larger sample sizes (N=100) do not yield perfectly replicable results.
  • The relationship between sample size and replicability demonstrates a clear need for increased sample sizes.

Conclusions:

  • Current sample sizes in task-based fMRI research are inadequate for ensuring robust replicability.
  • Larger sample sizes are essential for enhancing the reliability and validity of neuroimaging findings.
  • This study offers clear evidence supporting the necessity of larger sample sizes, aiming to be more accessible to the broader research community.