Frequency distribution, of data

Fig. 17 Frequency distribution of data for a sample concentration of 1 pg ml Target detection based on a single one second measurement gives TDER of 15.6%. Averaging over eight seconds reduces the TDER to 1.2% solid lines)...

TABLEal-2 Frequency Distribution of Data from Table al -1... 

Frequency domain performance, involving comparison of cumulative frequency distributions of the observed data and model predictions. In many situations, considering the various sources of error discussed earlier, it may... 

The objectives of this study are to determine the frequency distribution of radon levels in residential structures on a nationwide basis and to investigate factors which affect these levels. This study is needed to obtain a more accurate estimate of the average radon level in homes and to provide reliable data on the number of homes exceeding various radon levels. Such information will provide a better understanding of the magnitude of the public health problem associated with indoor radon levels. In addition this information will establish the base line level against which results of other surveys and indoor radon measurements can be compared. 

The only information presently available on the national frequency distribution of indoor radon levels is a 1984 analysis by Nero at the Lawrence Berkley Laboratory (Nero et al., 1984). Using data from about 500 houses, Nero developed a frequency distribution of radon levels in U.S. single family houses. This distribution is characterized by a geometric mean of 0.9 pCi/L and a geometric standard deviation of 2.8. 

However, since the data used in this study are subject to the limitations and uncertainties cited above, the results of this analysis represent only a very rough approximation of the national frequency distribution of indoor radon levels. EPA s national survey will seek to more accurately characterize this distribution through use of a larger sample size, a statistically based survey design, and consistent, quality assured sample collection and measurement procedures. 

The parameters of the frequency distributions of radon decay-product exposure are given in Table 3. This table combines the UK data from the national survey with those from local surveys. For the local surveys, the number of dwellings shown is fewer than the number surveyed actively, because only those that completed the follow-up passive survey have been included. 

Frequency distributions of indoor radon concentrations measured in Nagasaki, Hiroshima, Misasa and Mihama are shown in Figure 3. The data for these have approximately log-normal distributions. 

If we arrange all of our measurements of a particular variable in order as a point on an axis marked as to the values of that variable, and if our sample were large enough, the pattern of distribution of the data in the sample would begin to become apparent. This pattern is a representation of the frequency distribution of a given... 

A very different approach to characterize clustering tendency is based on the frequency distributions of the lengths of the edges in the minimum spanning tree connecting the objects in the real data and in uniformly distributed data (Forina et al. 2001). 

Figure 1 shows the noise level obtained with the maximum usable gain of 70 dB. Figure 2 is a F.F.T. of the time domain data of the previous figure. This shows the frequency distribution of the background noise. 

Prerequisite for the t-test is a normal distribution of data, i.e., the frequencies of data with the same deviation from mean forms a bell-shaped curve. In case of a large number of experimentally obtained data, mostly a Gaussian distribution is given. 

Figure 5. Frequency distribution of LAS concentrations below the 11,500 publicly owned treatment works in the United States under mean-flow and low-flow conditions plus ranked distribution of actual river-monitoring data. (Data are from ref 47.)...

For example, show the frequency distribution of the following data set that represents the number of students enrolled in 15 classes at Middleton Technical Institute ... 

Fig. 1.78.2. Frequency distribution of Tice in five runs [two runs together shown in (b)]. Data in Table 1.12.4...

A third and often neglected reason for the need for care fill application of chemometric methods is the problem of the type of distribution of environmental data. Most basic and advanced statistical methods are based on the assumption of normally distributed data. But in the case of environmental data, this assumption is often not valid. Figs. 1-7 and 1-8 demonstrate two different types of experimentally found empirical data distribution. Particularly for trace amounts in the environment, a log-normal distribution, as demonstrated for the frequency distribution of N02 in ambient air (Fig. 1-7), is typical. 

FIGURE 8.3 Frequency distribution of average phlorotannin concentrations of northeastern Pacific and Australasian rockweeds (Order Fucales) and kelps (Order Laminariales). Data are derived from a compilation of phlorotannin concentrations from the literature.19-24-25-29 31 33 35-37-39-41-42-78-141-150-151... 

Figure 2 Frequency distributions of debrisoquine metabolic ratios (MR) in four populations. An alignment of data from four separate studies. The abscissa indicates on a logarithmic scale the metabolic ratio debrisoquine/4-OH-debrisoquine in urine after administration of a test dose of debrisoquine these are conventional plots in which the increasing ratios reflect decreasing metabolism. The black bars indicate subjects classified as genetically poor metabolizers, usually defined as subjects with a metabolic ratio >12.6. Each of the four inserts represents an adaptation of a published illustration so that their abscissas are comparable and aligned for MR of unity. The insert marked China represents a study of 269 Han, Africa a study of 92 Venda, Sweden a study of 752 Swedes, and Spain a study of 377 Spaniards. The entry for Africa is marked with an asterisk because it represents tribal data of unknown generality. The measurements from China and Sweden were comparable, as ensured by controls. Source Compiled from Refs. 1, 99-101.

Probability distribution models can be used to represent frequency distributions of variability or uncertainty distributions. When the data set represents variability for a model parameter, there can be uncertainty in any non-parametric statistic associated with the empirical data. For situations in which the data are a random, representative sample from an unbiased measurement or estimation technique, the uncertainty in a statistic could arise because of random sampling error (and thus be dependent on factors such as the sample size and range of variability within the data) and random measurement or estimation errors. The observed data can be corrected to remove the effect of known random measurement error to produce an error-free data set (Zheng Frey, 2005). 

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