ci.median.ps: Confidence interval for a paired-samples median difference

In statpsych: Statistical Methods for Psychologists

Confidence interval for a paired-samples median difference

Description

Computes a distribution-free confidence interval for a difference of population medians in a paired-samples design. This function also computes the standard error of each median and the covariance between the two estimated medians. Tied scores within each measurement are assumed to be rare.

Usage

ci.median.ps(alpha, y1, y2)

Arguments

alpha	alpha level for 1-alpha confidence
y1	vector of scores for measurement 1
y2	vector of scores for measurement 2 (paired with y1)

Value

Returns a 1-row matrix. The columns are:

• Median1 - estimated median for measurement 1

• Median2 - estimated median for measurement 2

• Median1-Median2 - estimated difference of medians

• SE1 - standard error of median 1

• SE2 - standard error of median 2

• COV - covariance of the two estimated medians

• LL - lower limit of the confidence interval

• UL - upper limit of the confidence interval

References

\insertRef

Bonett2020statpsych

Examples

y1 <- c(21.1, 4.9, 9.2, 12.4, 35.8, 18.1, 10.7, 22.9, 24.0, 1.2, 6.1, 8.3, 13.1, 16.2)
y2 <- c(67.0, 28.1, 30.9, 28.6, 52.0, 40.8, 25.8, 37.4, 44.9, 10.3, 14.9, 20.2, 28.8, 40.6)
ci.median.ps(.05, y1, y2)

# Should return:
#  Median1 Median2 Median1-Median2       SE        LL        UL
#    12.75   29.85           -17.1 3.704248 -24.36019 -9.839807
#       SE1      SE2     COV
#  3.379695 4.968956 11.1957

statpsych documentation built on April 4, 2025, 3:20 a.m.