ci.median2: Confidence interval for a 2-group median difference

In statpsych: Statistical Methods for Psychologists

Confidence interval for a 2-group median difference

Description

Computes a distribution-free confidence interval for a difference of population medians in a 2-group design. Tied scores within each group are assumed to be rare.

For more details, see Section 2.12 of Bonett (2021, Volume 1)

Usage

ci.median2(alpha, y1, y2)

Arguments

alpha	alpha level for 1-alpha confidence
y1	vector of scores for group 1
y2	vector of scores for group 2

Value

Returns a 1-row matrix. The columns are:

• Median1 - estimated median for group 1

• Median2 - estimated median for group 2

• Median1-Median2 - estimated difference of medians

• SE - standard error

• LL - lower limit of the confidence interval

• UL - upper limit of the confidence interval

References

\insertRef

Bonett2002statpsych

\insertRef

Bonett2021statpsych

Examples

y1 = c(70, 394, 43, 95, 62, 128, 2, 203, 81, 436, 85, 35, 
        156, 1, 3, 27, 63, 181, 184, 18)
y2 = c(102, 120, 78, 78, 417, 124, 86, 171, 176, 129, 230, 
       194, 100, 157, 306, 411, 164, 103, 193, 312)
ci.median2(.05, y1, y2)

# Should return:
#  Median1 Median2 Median1-Median2       SE        LL        UL
#     75.5   160.5             -85 37.11502 -157.7441 -12.25589

statpsych documentation built on Jan. 13, 2026, 1:07 a.m.