mixtox (version 1.0)

NOEC: NOEC and LOEC Calculation

Description

Dunnett's test is used to calculate the NOEC and LOEC

Usage

NOEC(x, expr, sigLev = 0.05)

Arguments

x

a numeric vector of experimental concentrations

expr

a numeric matrix. each column is an experimental repetition and at least three repetitions are required.

sigLev

The significant level for Dunnett's test. The default is 0.05.

Value

• mat
  a matrix of experimental concentrations, Student's t-statistic, $F$ distribution at the sigLev, and sign (-1 or 1)
• no
  NOEC
• lo
  LOEC

Details

Dunnett's test (Dunnett, 1964) is performed by computing a Student's t-statistic for each experimental, or treatment, group where the statistic compares the treatment group to a single control group. Since each comparison has the same control in common, the procedure incorporates the dependencies between these comparisons. In particular, the t-statistics are all derived from the same estimate of the error variance which is obtained by pooling the sums of squares for error across all (treatment and control) groups. The formal test statistic for Dunnett's test is either the largest in absolute value of these t-statistics (if a two-tailed test is required), or the most negative or most positive of the t-statistics (if a one-tailed test is required).

References

Dunnett, C.W., 1964. New tables for multiple comparisons with a control. Biometrics 30, 482-491.

See Also

curveFit

Examples

data(cytotox)

## example 1
# calcualte the NOEC and LOEC of heavy metal Ni(2+) on the MCF-7 cells at the default significance 
# level of 0.05
x <- cytotox$Ni$x
expr <- cytotox$Ni$y
NOEC(x, expr)

## example 2
# calcualte the NOEC and LOEC of heavy metal Cu(2+) on the MCF-7 cells at the default significance
# level of 0.01
x <- cytotox$Cu$x
expr <- cytotox$Cu$y
NOEC(x, expr, sigLev = 0.01)