Random number table

Source Information compiled from Moody, J. R. Greenberg, R. R. Pratt, K. W. et al. Anal. Chem. 1988, 60, 1203A-1218A and Smith, B. W. Parsons, M. L. y, Chem. Educ. 1973, 50, 679-681. 

---

To analyze the properties of a 100 cm X 100 cm polymer sheet, ten 1 cm X 1 cm samples are to be selected at random and removed for analysis. Explain how a random number table can be used to ensure that samples are drawn at random. 

A shipment of 100 barrels of an organic solvent is to be evaluated by collecting and analyzing single samples from 10 of the barrels. A random number table is used to determine the barrels to be sampled. From which barrels should the samples be drawn if the first barrel is given by the twelfth entry in the random number table in Appendix IE, with subsequent barrels given by every third entry ... 

Randomization means that the sequence of preparing experimental units, assigning treatments, miming tests, taking measurements, and so forth, is randomly deterrnined, based, for example, on numbers selected from a random number table. The total effect of the uncontrolled variables is thus lumped together into experimental error as unaccounted variabiUty. The more influential the effect of such uncontrolled variables, the larger the resulting experimental error, and the more imprecise the evaluations of the effects of the primary variables. Sometimes, when the uncontrolled variables can be measured, their effect can be removed from experimental error statistically. 

Each zone is divided by an imaginary grid with units of approximately 4 meterA series of consecutive numbers is then assigned to the units of each grid. Through the use of a random numbers table, nj (for the Kth zone) of the grid units for sampling locations are selected, where... 

There are several methods for actually performing the randomization process. The three most commonly used are card assignment, use of a random number table, and use of a computerized algorithm. 

Perhaps the simplest algorithm for obtaining a randomized pairing of variables is the toss of a coin. However, to randomize the order of executing a larger series of measurements, one typically employs a random number generator or a random number table to assign random numbers to each of the measurements. 

To avoid bias and other sampling errors, the containers to be sampled must be randomly selected. To make a random selection, first number all containers in the lot, and then use a random number table (or computer generated set of random numbers) to choose from which container or containers to withdraw the samples. See Appendix I for an example on the use of random number tables. 

Pick the random number table page or generate the random numbers. 

Numbers from a random-number table were used to generate normal deviates. These were multiplied by as given above and the resulting synthetic errors were added to the to produce the experimental data. 

What advantage is there in using a random-number table or generator to determine which of the samples should be analysed ... 

A random sample means that every item in a population has an equal chance of being chosen. Simply choosing materials by eye does not satisfy this criterion. Each of the dose units should be assigned a number, starting at 1 and ending with the last number (i.e. the number of items in the sample). The materials to be chosen should then be picked by using either a computerized random-number generator or random-number tables. Whichever method is used, it should be documented. 

For relatively simple experiments, you can adopt a completely randomized design here, the position and treatment assigned to any subject is defined randomly. You ean draw lots, use a random number generator on a calculator, or use the random number tables which can be found in most books of statistical tables. 

All analysts have a personal preference for sampling patterns, and random number tables can eliminate this problem,... 

Both goals require obtaining a random sample. Here, the term random sample does not imply that the samples are chosen in a haphazard manner. Instead, a randomization procedure is applied to obtain such a sample. For example, suppose our sample is to consist of 10 pharmaceutical tablets to be drawn from 1000 tablets off a production line. One way to ensure a random sample is to choose the tablets to be tested from a table of random numbers. These can be conveniently generated from a random number table or from a spreadsheet, as shown in Figure 8-5. Here, we would assign each of the tablets a number from 1 to 1000 and use the sorted r andom numbers in column C of the spreadsheet to pick tablet 37, 71, 171, and so forth for analysis. 

In this case, it is also quite realistic to rely on non-cryptographic generation of r, e.g., using old random number tables. 

Randomization is a word which is used to describe the allocation at random (using aleatory devices, such as, for example, dice, cards, lots or random number tables or generators) of treatments to the units in an experiment. In a clinical trial these units are most typically the patients, although occasionally a centre might be treated as a unit, and in cross-over trials, in which patients may receive two or more treatments, a treatment episode is the basic experimental unit. 

Random sequences should be read from random number tables or, nowadays, these are read from a random number generator. This guarantees the genuine randomness of the sequence instead of subjective selections. 

Another approach considers four adjacent digits in the random number table. The first digit is the day identifier, with numbers 1 to 5 identifying the workday Monday through Friday. The second digit is the hour identifier, with numbers 0 to 8 added to the starting time of work (e.g., 7 00 a.m.). The third and fourth digits are the minutes identifiers, with numbers between 0 and 60 acceptable. 

Random-location storage, 1534, 1535 Randomness (in simulations), 2472-2473 Random normal deviates, 2386, 2389 Random numbers, table of, 2386, 2387 Random sampling, 1136 Random utility models, 2204 Range-of-joint mobility, 1043, 1046 Range-of-motion (ROM), 1064 Ranking method (job evaluation), 902-903 RAPID, 167... 

Selection of drivers must be made by a scientifically valid method. The Department of TVansportation (DOT) only recognizes a random number table or a computer-based random number generator that is matched with drivers Social Security numbers, payroll identification numbers, or other comparable identifying numbers as scientifically valid. Drawing names out of a hat is not considered scientifically valid. 

---