CI.mean: Confidence intervals for the mean

Description

CI.mean() builds confidence intervals for the mean of a population.

Usage

CI.mean(
  x,
  sigma = NULL,
  conf.level = 0.95,
  digits = 2,
  force.digits = FALSE,
  use.scientific = FALSE,
  data,
  ...
)

Value

A table reporting the confidence interval for the population mean. If the variance is unknown, the interval is built using percentiles from both the normal and the Student's t distribution.

Arguments

x: An unquoted string identifying the numeric variable whose mean is of interest. x can be the name of a vector in the workspace or the name of one of the columns in the data frame specified in the data argument.
sigma: An optional numeric value specifying the population standard deviation. If NULL (default) the population standard deviation is estimated using the data.
conf.level: Numeric value specifying the required confidence level; default to 0.95.
digits: Integer value specifying the number of decimals used to round statistics; default to 2. If the chosen rounding formats some non-zero values as zero, the number of decimals is increased so that all values have at least one significant digit, unless the argument force.digits is set to TRUE.
force.digits: Logical value indicating whether reported values should be forcedly rounded to the number of decimals specified in digits even if non-zero values are rounded to zero (default to FALSE).
use.scientific: Logical value indicating whether numbers in tables should be displayed using scientific notation (TRUE); default to FALSE.
data: An optional data frame containing x. If not found in data, x is taken from the environment from which CI.mean() is called.
...: Additional arguments to be passed to low level functions.

Author

Raffaella Piccarreta raffaella.piccarreta@unibocconi.it

Examples

Run this code

data(MktDATA, package = "UBStats")

# CI for the mean with KNOWN variance; default options
CI.mean(AOV, sigma = 30, data = MktDATA)

# CI for the mean with UNKNOWN variance;  
# - change digits and confidence level 0.99
CI.mean(AOV, conf.level = 0.99, digits = 3, data = MktDATA)

# Arguments force.digits and use.scientific
#  A variable taking very small values
SmallX<-MktDATA$AOV/5000 
#  - Default: manages possible excess of rounding
CI.mean(SmallX)
#  - Forcing digits to the default values (2)
CI.mean(SmallX, force.digits = TRUE)
#  - Allow scientific notation
CI.mean(SmallX, use.scientific = TRUE)

# Output the table with the requested interval
out.ci_mean<-CI.mean(AOV, data = MktDATA)