Adjustment Computations, 6th Edition

CHAPTER 2OBSERVATIONS AND THEIR ANALYSIS

2.1 INTRODUCTION

Sets of data can be represented and analyzed using either graphical or numerical methods. Simple graphical analyses to depict trends commonly appear in newspapers or on television. A plot of the daily variation of the closing Dow Jones industrial average over the past year is an example. A bar chart showing daily high temperatures over the past month is another. Also, data can be presented in numerical form and be subjected to numerical analysis. Instead of using the bar chart, the daily high temperatures could be tabulated and their mean computed. In surveying, observational data can also be represented and analyzed either graphically or numerically. In this chapter, some rudimentary methods for doing so are discussed.

2.2 SAMPLE VERSUS POPULATION

Due to time and financial constraints in statistical analyses, generally, only a small sample of data is collected from a much larger, possibly infinite population. For example, political parties may wish to know the percentage of voters who support their candidate. It would be prohibitively expensive to query the entire voting population to obtain the desired information. Instead, polling agencies select a subset of voters from the voting population. This is an example of population sampling.

As another example, suppose that an employer wishes to determine the relative ...