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Compares and combines slope coefficients in original and follow-up studies

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

This function computes confidence intervals for an OLS slope in a GLM from the original and follow-up studies, the difference in slopes, and the average of the slopes. Equality of error variances across studies is not assumed. The confidence interval for the difference uses a 1 - 2*alpha confidence level, which is recommended for equivalence testing. Use the replicate.gen function for slopes in other types of models (e.g., binary logistic, ordinal logistic, SEM). A Satterthwaite adjustment to the degrees of freedom is used to improve the accuracy of the confidence intervals for the average and the difference.

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

Usage

replicate.slope(alpha, b1, se1, n1, b2, se2, n2, s)

Arguments

alpha

alpha level for 1-alpha or 1 - 2alpha confidence

b1

sample slope in original study

se1

standard error of slope in original study

n1

sample size in original study

b2

sample slope in follow-up study

se2

standard error of slope in follow-up study

n2

sample size in follow-up study

s

number of predictor variables in model

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 slopes

  • Row 4 estimates the average slope

The columns are:

  • Estimate - slope 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.slope(.05, 23.4, 5.16, 50, 18.5, 4.48, 90, 4)
#>                       Estimate       SE     t     p        LL       UL    df
#> Original:                23.40 5.160000 4.535 0.000 13.007227 33.79277  45.0
#> Follow-up:               18.50 4.480000 4.129 0.000  9.592560 27.40744  85.0
#> Original - Follow-up:     4.90 6.833447 0.717 0.475 -6.438743 16.23874 106.4
#> Average:                 20.95 3.416724 6.132 0.000 14.176310 27.72369 106.4

# Should return: 
#                       Estimate       SE     t     p        LL       UL    df
# Original:                23.40 5.160000 4.535 0.000 13.007227 33.79277  45.0
# Follow-up:               18.50 4.480000 4.129 0.000  9.592560 27.40744  85.0
# Original - Follow-up:     4.90 6.833447 0.717 0.475 -6.438743 16.23874 106.4
# Average:                 20.95 3.416724 6.132 0.000 14.176310 27.72369 106.4