ci.phi {statpsych}

Confidence interval for a phi correlation

Description

Computes a Fisher confidence interval for a population phi correlation. This function requires the frequency counts from a 2 x 2 contingency table for two dichotomous variables. This measure of association is usually most appropriate when both dichotomous variables are naturally dichotomous.

Usage

ci.phi(alpha, f00, f01, f10, f11)

Arguments

alpha

alpha level for 1-alpha confidence

f00

number of participants with y = 0 and x = 0

f01

number of participants with y = 0 and x = 1

f10

number of participants with y = 1 and x = 0

f11

number of participants with y = 1 and x = 1

Value

Returns a 1-row matrix. The columns are:

• Estimate - estimate of phi correlation

• SE - standard error

• LL - lower limit of the confidence interval

• UL - upper limit of the confidence interval

References

Bishop YMM, Fienberg SE, Holland PW (1975). Discrete Multivariate Analysis. MIT Press.

Examples

ci.phi(.05, 229, 28, 96, 24)

# Should return:
#  Estimate         SE         LL        UL
#  0.1229976 0.05477117 0.01462398 0.2285149