ci.stdmean2: Confidence intervals for a 2-group standardized mean...

In statpsych: Statistical Methods for Psychologists

Confidence intervals for a 2-group standardized mean difference

Description

Computes confidence intervals for a population standardized mean difference. Unweighted, weighted, and single group variance standardizers are used. The square root weighted variance standardizer is recommended in 2-group nonexperimental designs with simple random sampling. The square root unweighted variance standardizer is recommended in 2-group experimental designs. The single group standard deviation standardizer can be used with experimental or nonexperimental designs. Equality of variances is not assumed.

Usage

ci.stdmean2(alpha, m1, m2, sd1, sd2, n1, n2)

Arguments

alpha	alpha level for 1-alpha confidence
m1	estimated mean for group 1
m2	estimated mean for group 2
sd1	estimated standard deviation for group 1
sd2	estimated standard deviation for group 2
n1	sample size for group 1
n2	sample size for group 2

Value

Returns a 4-row matrix. The columns are:

• Estimate - estimated standardized mean difference

• adj Estimate - bias adjusted standardized mean difference estimate

• SE - standard error

• LL - lower limit of the confidence interval

• UL - upper limit of the confidence interval

References

\insertRef

Bonett2008statpsych

Examples

ci.stdmean2(.05, 35.1, 26.7, 7.32, 6.98, 30, 30)

# Should return:
#                          Estimate  adj Estimate        SE        LL       UL
# Unweighted standardizer: 1.174493      1.159240 0.2844012 0.6170771 1.731909
# Weighted standardizer:   1.174493      1.159240 0.2802826 0.6251494 1.723837
# Group 1 standardizer:    1.147541      1.117605 0.2975582 0.5643375 1.730744
# Group 2 standardizer:    1.203438      1.172044 0.3120525 0.5918268 1.815050

statpsych documentation built on Sept. 11, 2024, 7:42 p.m.