Metrohm tiamo 2.1 Manual - Manual (Page 78)

2.4 Formula editor ￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭
64 ￭￭￭￭￭￭￭￭ tiamo 2.1
Type number, value range: 1 ... n. Direct entry as number or as formula
providing a number. If the type of value is non-permitted, then the result
will become invalid. The number of independent samplings for calculating
the standard deviation, reduced by the number of adjusted parameters for
the model to which the standard deviation refers, must be specified as
degrees of freedom (Degrees of freedom = Number of samplings
− Number
of parameters).
Examples
Tinv(0.95; 9) = 2.26 : With a 10-fold determination (e.g. of a titer) half
the interval length corresponds to 2.26 times the standard deviation.
Calculation of the confidence interval for a mean value of sam-
pling: A variance-homogenous sampling with a range n for a normally
distributed quantity with an expected value µ has the mean value x
m
, the
standard deviation s and the freedom degrees v = n − 1. Half the interval
length t
s
⋅ s/√ n then indicates how high the absolute difference between
the mean value x
m
and the expected value µ maximally is within the given
probability. The confidence interval is the full interval length, centered to
the mean value: µ = x
m
± t
s
⋅ s/√ n.
Titer determination: 0.991, 1.021, 0.995, 1.003, 1.007, 0.993, 0.998,
1.015, 1.003, 0.985
Mean value = 1.001
Standard deviation = 0.0111
Student's t-quantiles for a probability of 95% = 2.26
Confidence interval of the titer = 1.001 ± 0.008
2.4.4.6 Date/time functions
2.4.4.6.1 Time()
Dialog window: Formula editor ▶ Operators/Functions
Syntax
y = Time()
Gives the current date and the current time.
Parameters
none
Return value
Current date and current time in the format yyyy-mm-dd hh:mm:ss UTC
±xx