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Compares and combines 2-group mean differences in original and follow-up studies

Source: R/meta_rep.R
replicate.mean2.Rd

This function computes confidence intervals from an original study and a follow-up study where the effect size is a 2-group mean difference. Confidence intervals for the difference and average effect size are also computed. Equality of variances within or across studies is not assumed. A Satterthwaite adjustment to the degrees of freedom is used to improve the accuracy of the confidence intervals. The confidence level for the difference is 1 – 2*alpha, which is recommended for equivalence testing.

For more details, see Chapter 4 of Bonett (2021, Volume 5).

Usage

replicate.mean2(
  alpha,
  m11,
  m12,
  sd11,
  sd12,
  n11,
  n12,
  m21,
  m22,
  sd21,
  sd22,
  n21,
  n22
)

Arguments

alpha

alpha level for 1-alpha confidence

m11

estimated mean for group 1 in original study

m12

estimated mean for group 2 in original study

sd11

estimated SD for group 1 in original study

sd12

estimated SD for group 2 in original study

n11

sample size for group 1 in original study

n12

sample size for group 2 in original study

m21

estimated mean for group 1 in follow-up study

m22

estimated mean for group 2 in follow-up study

sd21

estimated SD for group 1 in follow-up study

sd22

estimated SD for group 2 in follow-up study

n21

sample size for group 1 in follow-up study

n22

sample size for group 2 in follow-up study

Value

A 4-row matrix. The rows are:

  • Row 1 summarizes the original study

  • Row 2 summarizes the follow-up study

  • Row 3 estimates the difference in mean differences

  • Row 4 estimates the average mean difference

The columns are:

  • Estimate - mean difference estimate (single study, difference, average)

  • SE - standard error

  • t - t-value

  • p - p-value

  • LL - lower limit of the confidence interval

  • UL - upper limit of the confidence interval

  • df - degrees of freedom

References

Bonett DG (2021). “Design and analysis of replication studies.” Organizational Research Methods, 24(3), 513–529. ISSN 1094-4281, doi:10.1177/1094428120911088 .

Bonett DG (2021). Statistical Methods for Psychologists, Vol 1-5, https://dgbonett.sites.ucsc.edu/.

Examples

replicate.mean2(.05, 21.9, 16.1, 3.82, 3.21, 40, 40, 
                     25.2, 19.1, 3.98, 3.79, 75, 75)
#>                       Estimate        SE      t     p        LL       UL     df
#> Original:                 5.80 0.7889312  7.352 0.000  4.228624 7.371376  75.75
#> Follow-up:                6.10 0.6346075  9.612 0.000  4.845913 7.354087 147.65
#> Original - Follow-up:    -0.30 1.0124916 -0.296 0.767 -1.974571 1.374571 169.16
#> Average:                  5.95 0.5062458 11.753 0.000  4.950627 6.949373 169.16

# Should return:
#                       Estimate        SE      t     p        LL       UL     df
# Original:                 5.80 0.7889312  7.352 0.000  4.228624 7.371376  75.75
# Follow-up:                6.10 0.6346075  9.612 0.000  4.845913 7.354087 147.65
# Original - Follow-up:    -0.30 1.0124916 -0.296 0.767 -1.974571 1.374571 169.16
# Average:                  5.95 0.5062458 11.753 0.000  4.950627 6.949373 169.16