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Statistics
Midterm Exam
21
Chemistry
Undergraduate 1
02/27/2010

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Term
accuracy
Definition
a measure of how close a measured value is to the "true" value
Term
determinate error
Definition
error due to procedural or instrumental factors that cause a measurement to be consistently too large or too small. the error can, in principle, be discovered and corrected (also called systematic error)
Term
indeterminate error
Definition
a type of error, which can be either positive or negative and cannot be eliminated, based on the ultimate limitations on a physical measurement (also called random error)
Term
precision
Definition
a measure of the reproducibility of a measurement
Term
relative error
Definition
Term
relative precision (rsd)
Definition
a measure of the precision of a measurement
Term
significant figure
Definition
the number of significant digits in a quantity is the minimum number of digits needed to express the quantity in scientific notation. in experimental data, the first uncertain figure is the last significant figure.
Term
degrees of freedom
Definition
in statistics, the number of independent observations upon which a result is based
Term
confidence interval
Definition
the range of values within which there is a specified probability that the true value will be found
Term
confidence level
Definition
Term
Gaussian distribution
Definition
theoretical bell-shaped distribution of measurements when all error is random. the center of the curve is the mean and the width is characterized by the standard deviation. a normalized curve is also called the "normal curve"
Term
mean
Definition
the average of a set of all results
Term
median
Definition
for a set of data, that value above and below which there are equal numbers of data
Term
range
Definition
the difference between the highest and lowest values in a set of data; also called "spread." with respect to an analytical method, it is the concentration interval over which the linearity, accuracy, and precision are all acceptable.
Term
standard deviation
Definition
a statistic measuring how closely data are clustered about the mean value.
Term
pooled standard deviation
Definition
Term
Q test
Definition
Term
Grubbs test
Definition
statistical test used to decide whether to discard a datum that appears discrepant
Term
t statistic
Definition
statistical test used to decide whether the results of two experiments are within experimental uncertainty of each other. the uncertainty must be specified to within a certain probability.
Term
student's t test
Definition
a statistical tool used to express confidence intervals to compare results from different experiments
Term
variance
Definition
the square of standard deivation
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