Abstract
The existing -test for correlated proportions under classical statistics is applied when observations in the data are exact and precise. In the current paper, -test for correlated proportions is proposed to deal with the data having indeterminate observations. The statistic of -test for correlated proportions under neutrosophy is introduced in the paper. The testing procedure of the proposed test is given. The application of the proposed test is given using the price of oil data. From the application, it is clear that the proposed test outperforms the existing -test for correlated proportions under classical statistics in terms of flexibility, adequacy, and information. The simulation study also shows the effect of indeterminacy on the statistic of the proposed test.
1. Introduction
The Z-test is a statistical test that is used to see the differences between two population variances are equal or not. This test is applied under the assumption that the data are obtained from the normal population and samples are independent. The -test for correlated proportions is applied to investigate the difference between two correlated proportions. The -test for correlated proportions is applied to test the null hypothesis that proportions of two populations are the same vs. the alternative hypothesis that there is a significant difference between two population proportions. The Z-test has the limitation that it is applied when the sample size is greater than thirty. The authors of [1–4] and [5] worked on the applications of statistical tests.
The statistical tests under classical statistics may mislead if the observations in the data are indeterminate, imprecise, and fuzzy. Viertl [6] mentioned that “statistical data are frequently not precise numbers but more or less nonprecise, also called fuzzy. Measurements of continuous variables are always fuzzy to a certain degree.” The fuzzy-based statistical tests are considered quite adequate to deal with fuzzy data. The authors of [7–14] and [15] presented excellent work on statistical tests using fuzzy logic.
The neutrosophic statistics as an extension of classical statistics was introduced in [16] using the idea of neutrosophic logic introduced in [17]. The efficiency of neutrosophic logic was discussed in [18]. The authors of [19–21] [22, 23] applied neutrosophic logic to deal with real problems. The authors of [24–29] and [30] used neutrosophic statistics to analyze uncertain, indeterminate, and interval data. More details on neutrosophic statistics can be seen in [31].
The existing -test for correlated proportions under classical statistics cannot be applied for testing in the presence of uncertainty, indeterminacy, and neutrosophy in the data. The -test for correlated proportions under neutrosophic statistics should be introduced to analyze such a type of data. In this paper, the Z-test for correlated proportions under indeterminacy is introduced. The neutrosophic statistic for the proposed test is also introduced. The necessary steps to carry out the proposed test are given. The proposed test is analyzed using the oil payoff data. With the application and simulation studies, it is expected that the proposed test will be flexible, informative, and adequate in uncertainty.
2. Proposed Test
In case of uncertainty and indeterminacy in the observations, the existing -test for correlated proportions cannot be applied for testing the significant differences between two population proportions. In this section, -test for correlated proportions will be designed when the data are imprecise, indeterminate, and neutrosophic under the assumption that the neutrosophic sample is quite large. The general form of contingency table having imprecise, indeterminate, and neutrosophic observations is introduced in Table 1.
In Table 2, the first part of the neutrosophic form presents the classical statistics (determined part) and the second part shows the indeterminate part with an associated measure of indeterminacy. To test the hypothesis that there is a difference between two population proportions, the neutrosophic statistic is defined aswhere is defined as
The neutrosophic form of statistic is defined as
The neutrosophic form of consists of two parts namely the determined part and indeterminate part. The first part denotes the determined part and denotes the indeterminate part. Note that is a measure of indeterminacy associated with the statistic . The proposed test statistic reduces to statistic under classical statistics when .
3. Application Using Oil Price Data
The application of the proposed test is given using the data of crude oil prices. For the application, five states, stock A, and stock B are chosen. Two categories are : price is decreased by 1%-2% and : the price is increased by 1%-2%. The data are taken from [32] and reported in Table 3. The neutrosophic form of the payoff data is shown in Table 4. The decision maker is interested to investigate the difference between the proportions of prices in two stocks. From the fuzzy payoff matrix for stock A and stock B in Table 3, it can be seen that the payoff data is in the interval; therefore, the existing test under classical statistics cannot be applied to test the null hypothesis : the difference between the two correlated proportions is insignificant vs. the alternative hypothesis : the difference between the two correlated proportions is significant. The proposed test is quite adequate to be applied for testing vs. for the given data. The constant for the given data is calculated as
The neutrosophic statistic for the given data is calculated as
The neutrosophic form of statistic is given as . The proposed test can be implemented in the following steps. Step 1 (state ): no difference between proportions of prices in two stocks vs. : difference exist between proportions of prices in two stocks Step 2: let the level of significance = 5% and the tabulated critical value be 1.96 Step 3: we do not reject as .
The operational procedure of the proposed test for the real example is also shown in Figure 1.

4. Comparative Study
The proposed test is a generalization of the existing -test for correlated proportions under classical statistics. The proposed test reduces to the classical test when no vague values are recorded in the data. The efficiency of the proposed -test for correlated proportions under neutrosophic statistics is compared with the existing -test for correlated proportions under classical statistics in terms of a measure of vagueness. The neutrosophic form of statistic is , where the first value 0.0062 presents the value of statistic under classical statistics and the second part shows the indeterminate part. Note that is the measure of vagueness associated with the statistic . From the neutrosophic form, it is clear that the proposed statistic has a lower value, that is, 0.0062 and an upper value, that is, 0.0065. The proposed test statistic is expressed in indeterminate interval rather than the exact value. In testing of hypothesis, when the data are given in interval, the decision makers can expect the value from 0.0062 to 0.0065. On the contrary, the existing test gives only a single (exact) value which is not adequate in uncertainty. From this comparison, it can be concluded that the proposed test is elastic than the existing -test for correlated proportions. Now, the comparison of the proposed test will be given in terms of a measure of indeterminacy. For testing the hypothesis when the probability of committing a type-I error is 0.05, the proposed test is interpreted as follows: the probability of accepting is 0.95, the probability of committing an error is 0.05, and the measure of vagueness is 0.05. From the analysis, it is clear that the proposed test gives additional information about the measure of vagueness. Based on the analysis, it can be concluded that the proposed test is adequate, informative, and elastic than the existing -test for correlated proportions.
5. Simulation Study
In this section, the simulation study is carried to see the effect of indeterminacy on the statistic . The various values of are taken to see the effect of indeterminacy on the statistic . The values of statistic for various are shown in Table 5. From Table 5, it can be seen that = 0.0062 when = 0. It is interesting note that, as the values of is increased from 0 to 1, the values of is also increased. It means that the indeterminacy parameter affects the values of . From this study, it is concluded that the decision makers should be careful in applying the test under uncertainty.
6. Concluding Remarks
The existing -test for correlated proportions under classical statistics is applied when observations in the data are exact and precise. In the current paper, -test for correlated proportions was proposed to deal with the data having indeterminate observations. The statistic of -test for correlated proportions under neutrosophy was introduced in the paper. The proposed test was a generalization of the exiting -test for correlated proportions and applied when the data are in intervals. The real example and the comparative study show that the proposed test is efficient than the existing -test for correlated proportions in terms of flexibility, adequacy, and information. The proposed test for big data can be studied as future research.
Data Availability
The data used to support the findings of the study are provided within the article.
Conflicts of Interest
The authors declare that there are no conflicts of interest.
Acknowledgments
This work was funded by the Deanship of Scientific Research (DSR), King Abdulaziz University, Jeddah, under Grant no. D-179-130-1439. The authors, therefore, gratefully acknowledge the DSR technical and financial support.