Skip to contents

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

Source: R/meta_rep.R
replicate.meanratio2.Rd

This function computes confidence intervals from an original study and a follow-up study where the effect size is a 2-group mean ratio. Confidence intervals for the log-difference and average log 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.meanratio2(
  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, Price RM (2020). “Confidence intervals for ratios of means and medians.” Journal of Educational and Behavioral Statistics, 45(6), 750–770. ISSN 1076-9986, doi:10.3102/1076998620934125 .

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

Examples

replicate.meanratio2(.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     df
#> Original:             0.30766736 0.04188600  7.3454 0.00000  76.65
#> Follow-up:            0.27715566 0.02928438  9.4643 0.00000 140.91
#> Original - Follow-up: 0.03051171 0.05110785  0.5970 0.55141 150.35
#> Average:              0.29241151 0.02555393 11.4429 0.00000 150.35
#>                       exp(Estimate)   exp(LL)  exp(UL)
#> Original:                  1.360248 1.2513908 1.478576
#> Follow-up:                 1.319372 1.2451576 1.398009
#> Original - Follow-up:      1.030982 0.9473616 1.121983
#> Average:                   1.339654 1.2736927 1.409032

# Should return:
#                         Estimate         SE       t       p     df
# Original:             0.30766736 0.04188600  7.3454 0.00000  76.65
# Follow-up:            0.27715566 0.02928438  9.4643 0.00000 140.91
# Original - Follow-up: 0.03051171 0.05110785  0.5970 0.55141 150.35
# Average:              0.29241151 0.02555393 11.4429 0.00000 150.35
#                       exp(Estimate)   exp(LL)  exp(UL)
# Original:                  1.360248 1.2513908 1.478576
# Follow-up:                 1.319372 1.2451576 1.398009
# Original - Follow-up:      1.030982 0.9473616 1.121983
# Average:                   1.339654 1.2736927 1.409032