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.

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

Examples

y1 <- c(32.1, 39.8, 26.3, 35.0, 43.1, 27.0, 40.9, 37.4, 34.0, 29.2)
y2 <- c(36.8, 44.0, 47.1, 42.7, 49.0, 39.6, 46.2, 31.6, 33.1, 48.4)
ci.median2(.05, y1, y2)

# Should return:
#  Median1 Median2 Median1-Median2       SE        LL         UL
#     34.5   43.35           -8.85 4.494993 -17.66002 -0.0399751

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