Statics Flashcards

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Definitions and Formulas
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1

What is the definition of an average?

The sum of several values divided by the number of values. Also called mean.

2

What is the definition of a blank?

A sample not intended to contain analyte

3

What is the definition of a calibration curve?

A graph showing the value of some property versus concentration of analyte. When the corresponding property of an unknown is measured, its concentration can be determined from the graph. Also called standard curve

4

What is the definition of a confidence interval?

The range of values within which there is a specified probability that the “true” value will be found

5

What is the definition of an F test?

For two variances, s2 1 and s2 2 (with s1 chosen to be the larger of the two), the statistic F is defined as F = [s2 1 /s2 2.] To decide whether s1 is significantly greater than s2, we compare F with the critical values in a table based on a certain confidence level. If the calculated value of F is greater than the value in the table, the difference is significant.

6

What is the definition of a Gaussian distribution?

Theoretical bell-shaped distribution of measurements when all error is random. The center of the curve is the mean (μ) and the width is characterized by the standard deviation (σ). A normalized Gaussian distribution, also called the normal error curve, has an area of unity and is given by

7

What is the definition of a Grubbs test?

Statistical test used to decide whether to discard a datum that appears discrepant

8

What is the definition of a mean?

The sum of a set of results divided by the number of values in the set. Also called average.

9

What is the definition of a a median?

For a set of data, that value above and below which there are equal numbers of data.

10

What is the definition of a method of least squares?

Process of fitting a mathematical function to a set of measured points by minimizing the sum of the squares of the distances from the points to the curve

11

What is the definition of a range?

The difference between the highest and lowest values in a set of data. Also called spread. With respect to an analytical method, range is the concentration interval over which linearity, accuracy, and precision are all acceptable.

12

What is the definition of a slope?

For a straight line whose equation is y = mx + b, the value of m is the slope. It is the ratio Δy/Δx for any segment of the line.

13

What is the definition of a standard deviation?

A statistic measuring how closely data are clustered about the mean value. For a finite set of data, the standard deviation, s, is computed from the formula

14

What is the definition of a standard solution?

A solution whose composition is known by virtue of the way that it was made from a reagent of known purity or by virtue of its reaction with a known quantity of a standard reagent.

15

What is the definition of a Student’s t?

A statistical tool used to express confidence intervals and to compare results from different experiments

16

What is the definition of a t test?

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.

17

What is the definition of a variance?

The square of the standard deviation.

18

What is the definition of a y-intercept?

The value of y at which a line crosses the y-axis.

19

What is a Determinate error?

also called systematic error, arises from procedural or instrumental factors that make a measurement consistently too large or too small. With care, it can be eliminated.

20

What is a random error?

arises from physical limitations of measurements. It is equally likely to be positive or nega- tive, and it cannot be completely eliminated.