vcmeta (version 1.5.0)

replicate.slope: Compares and combines slope coefficients in original and follow-up studies

Description

This function computes confidence intervals for a slope 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.

Usage

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

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

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

References

Bonett2021vcmeta

Examples

replicate.slope(.05, 23.4, 5.16, 50, 18.5, 4.48, 90, 4)

# Should return: 
#                       Estimate       SE         t            p
# Original:                23.40 5.160000 4.5348837 4.250869e-05
# Follow-up:               18.50 4.480000 4.1294643 8.465891e-05
# Original - Follow-up:     4.90 6.833447 0.7170612 4.749075e-01
# Average:                 20.95 3.416724 6.1316052 1.504129e-08
#                              LL       UL       df
# Original:             13.007227 33.79277  45.0000
# Follow-up:             9.592560 27.40744  85.0000
# Original - Follow-up: -6.438743 16.23874 106.4035
# Average:              14.176310 27.72369 106.4035