prec_meandiff | R Documentation |
prec_meandiff
returns the sample size or the precision for the
provided mean difference and standard deviations. For paired differences, use
prec_mean
, as it is equivalent to a simple mean.
prec_meandiff( delta, sd1, sd2 = sd1, n1 = NULL, r = 1, conf.width = NULL, conf.level = 0.95, variance = c("equal", "unequal"), ... )
delta |
difference in means between the two groups. |
sd1 |
standard deviation in group 1. |
sd2 |
standard deviation in group 2. |
n1 |
number of patients in group 1. |
r |
allocation ratio (relative size of group 2 and group 1 (n2 / n1)). |
conf.width |
precision (the full width of the confidence interval). |
conf.level |
confidence level. |
variance |
|
... |
other options to uniroot (e.g. |
Exactly one of the parameters n
or conf.width
must be passed as NULL,
and that parameter is determined from the other.
Object of class "presize", a list of arguments (including the computed one) augmented with method and note elements.
# mean difference of 5, SD of 2.5, CI width with 20 participants assuming equal variances prec_meandiff(delta = 5, sd1 = 2.5, n1 = 20, var = "equal") # mean difference of 5, SD of 2.5, number of participants for a CI width of 3, # assuming equal variances prec_meandiff(delta = 5, sd1 = 2.5, conf.width = 3, var = "equal")
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