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preface to fifteenth edition

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GENERAL INFORMATION, CONVERSION TABLES, AND MATHEMATICS 2.117<br />

x 2c 3x<br />

f(x) 1⁄2a 0 a1 cos a2 cos a3<br />

cos ···<br />

c c c<br />

x 2x 3x<br />

b1 sin b2 sin b3<br />

sin ···<br />

c c c<br />

where the constant coefficients are determined as follows:<br />

<br />

c<br />

c<br />

1 nt 1 nt<br />

n<br />

an<br />

f(t) cos dt b f(t) sin dt<br />

c c c c c c<br />

In case the curve y f(x) is symmetrical with respect <strong>to</strong> the origin, the a’s are all zero, and the<br />

series is a sine series. In case the curve is symmetrical with respect <strong>to</strong> the y axis, the b’s are all zero,<br />

and a cosine series results. (In this case, the series will be valid not only for values of x between<br />

c and c, but also for x c and x c.) A Fourier series can always be integrated term by term;<br />

but the result of differentiating term by term may not be a convergent series.<br />

<br />

TABLE 2.25<br />

Some Constants<br />

Constant Number Log 10 of Number<br />

Pi () 3.14159 26535 89793 23846 0.49714 98726 94133 85435<br />

Napierian Base (e) 2.71828 18284 59045 23536 0.43429 448<br />

M log10e<br />

0.43429 44819 03251 82765 9.63778 43113 00536 78912 10<br />

1 M log e 10 2.30258 50929 94045 68402 0.36221 569<br />

180 degrees in 1 radian 57.2957 795 1.75812 263<br />

180 radians in 1 0.01745 329 8.24187 737 10<br />

10800 radians in 1 0.00029 08882 6.46372 612 10<br />

648000 radians in 1 0.00000 48481 36811 095 4.68557 487 10<br />

2.3 STATISTICS IN CHEMICAL ANALYSIS<br />

2.3.1 Introduction<br />

Eachobservation in any branchof scientific investigation is inaccurate <strong>to</strong> some degree. Often the<br />

accurate value for the concentration of some particular constituent in the analyte cannot be determined.<br />

However, it is reasonable <strong>to</strong> assume the accurate value exists, and it is important <strong>to</strong> estimate<br />

the limits between which this value lies. It must be unders<strong>to</strong>od that the statistical approach is concerned<br />

with the appraisal of experimental design and data. Statistical techniques can neither detect<br />

nor evaluate constant errors (bias); the detection and elimination of inaccuracy are analytical problems.<br />

Nevertheless, statistical techniques can assist considerably in determining whether or not<br />

inaccuracies exist and in indicating when procedural modifications have reduced them.<br />

By proper design of experiments, guided by a statistical approach, the effects of experimental<br />

variables may be found more efficiently than by the traditional approach of holding all variables<br />

constant but one and systematically investigating eachvariable in turn. Trends in data may be sought<br />

<strong>to</strong> track down nonrandom sources of error.

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