Translucidez de las resinas compuestas dentales

Pyrite provided data on a total of 2,122 unplanned outage incidents to the researcher. Of these, a total of 85 incidents (four percent of those provided) were eliminated from the total analysed for one of four reasons. One reason incidents were eliminated was when the incident number provided was not unique. This indicated that duplicate instances of the same incident were sent. A review of each of those items for which duplicate incident numbers were identified confirmed that the data associated with duplicate incident numbers were, in fact, duplicate instances of the same incident. Only the duplicate incidents were eliminated. A single instance of the incident was retained and the duplicate incidents (N = 42) were eliminated from the data analysed. A second reason incidents were eliminated was because the severity of the incident was not identified (N = 26). The severity of the incident was a required field (as indicated in Table 4-3). Thirdly, incidents that were not completed or not closed and had no valid ―close date‖ or no valid ―close time‖ were eliminated (N = 16) from data analysis because the incident had not been reported as restored. Given that no restoration date or restoration time was provided, no valuable restoration data could be obtained from the incident information provided. The final reason an unplanned outage

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provided by Pyrite was not included in the analysis performed was that, although it met all the criteria required for analysis, there was only one report of a Systems Overload unplanned outage. It was eliminated because of inadequate data. Although a total of 85 of the incidents provided by Pyrite were eliminated from those analysed, 95.99 percent (N = 2,036) of the unplanned outage data provided by Pyrite was used and analysed.

Of those 2,036 unplanned outages, all were viable and used in the data analysis performed on the unplanned outage data provided by Pyrite. In total, there were 950 unplanned Hardware outages (46.6 percent of those incidents analysed), 139 unplanned Humans Inside the Affected Company outages (6.8 percent of those incidents analysed), and 947 unplanned Software outages (46.5 percent of those incidents analysed).

Of the seven possible types of outages (Acts of Nature, Hardware, Humans Inside the Affected Company, Humans Outside the Affected Company, Software, System Overload, and Vandalism) that could have been included in the inventory of unplanned outages analysed, only four types of those outages were actually included. There were no reports of unplanned outages due to Acts of Nature; there were no reports of unplanned outages due to Humans Outside the Affected Company; there were no reports of unplanned outages due to Vandalism. Moreover, there was only one System Overload unplanned outage reported, representing only 0.0005 percent of the unplanned outages provided by Pyrite; it was eliminated from the data analysed. A descriptive analysis performed on the unplanned outage data that was included in the researcher‘s analysis to establish initial information about the data is depicted in Table 5-16.

Table 5-16. Descriptive Analysis – Unplanned Outage Types

Company 139 1214.77 3941.71 1.00 29523.48 13.00 0.84

Software 947 3037.63 7500.79 1.15 65110.80 285.40 2.11

Total Unplanned

Outages 2036 2253.73 6934.70 0.77 108068.00 136.83

1.56

To determine the acceptability of Hypothesis 5, that there will be a significant difference between unplanned outage types and their Mean Times to Restore Service, further analysis was undertaken. A Kruskal-Wallis test was performed on the unplanned outage data

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provided by Pyrite to determine if statistically significant differences could be found between the unplanned outage types and the MTRS attained. This non-parametric test is based on the assumption that the population tested is not normally distributed; however, it does assume an identically shaped and scaled distribution for each group. It is, effectively, ANOVA for testing the equality of population medians among groups (with data replaced by ranks). Results of the Kruskal-Wallis test are shown in Table 5-17.

Table 5-17. Kruskal-Wallis Test: Unplanned Outages and MTRS Kruskal-Wallis Test: Unplanned Outage Types and Associated MTRS

Unplanned Outage Type N Mean Rank

MTRS

Hardware 950 930.81

Humans Inside the Affected Company 139 643.04

Software 947 1161.58

Total Number of Unplanned Outages 2036

Chi-Square 133.92

DF 2.00

P-Value 0.00

Hypothesis 5, there is a significant difference between unplanned outage types and their Mean Times to Restore service, with a p value of < 0.01, is accepted.

Further testing was conducted to determine the relationships between individual outage types and their respective Mean Times to Restore Service. The Kolmogorov-Smirnov test was performed for the pairs Hardware-Software, Hardware-Humans Inside the Affected Company, and Software-Humans Inside the Affected Company. Hypothesis 5 is accepted, as each of the p values is < 0.01. (See Tables 5-18, 5-19, and 5-20, respectively.)

Table 5-18. Kolmogorov-Smirnov Test: Hardware-Software and MTRS Kolmogorov-Smirnov Test: Unplanned Hardware-Software Outages and Associated MTRS

Unplanned Outage^a Type N MTRS

Hardware 950

Software 947

Total Number of Unplanned Outages of these types 1897

TEST Kolmogorov-Smirnov 3.85

P-Value 0.00

a Grouping Variable: Unplanned Outage Type

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Table 5-19. Kolmogorov-Smirnov Test: Hardware-Humans and MTRS

Kolmogorov-Smirnov Test: Unplanned Hardware-Humans-In-the-Affected-Company Outages and Associated MTRS

Unplanned Outage^a Type N MTRS

Hardware 950

Human Inside Affected Company 139

Total Number of Unplanned Outages of these types 1089

TEST Kolmogorov-Smirnov 4.44

P-Value 0.00

a Grouping Variable: Unplanned Outage Type

Table 5-20. Kolmogorov-Smirnov Test: Software-Humans and MTRS

Kolmogorov-Smirnov Test: Unplanned Software- Humans-Inside-the-Affected-Company Outages and Associated MTRS

Unplanned Outage^a Type N MTRS

Software 947

Human Inside Affected Company 139

Total Number of Unplanned Outages of these types 1086

TEST Kolmogorov-Smirnov 5.08

P-Value 0.00

a Grouping Variable: Unplanned Outage Type

Figure 5-3, a box plot generated using SPSS™ Version 15, displaying a five-value summary of the distribution, depicts the horizontal line in each box as the median value of the attained MTRS value. The horizontal lines below and above the medians are the 25^th and 75^th percentile values, respectively. The two whiskers at the bottom and top are the minimum and maximum values of the distribution. The extreme outliers are shown above the top whisker. An analysis of the box and whisker plot clearly demonstrates that the median values of the MTRS for different types of unplanned outages analysed in this research were different from one another.

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Figure 5-3. Box and Whisker Plots Display the Relationship Between Unplanned Outage Types and Their Associated Mean Times to Restore Service. (The Natural Logarithm of the MTRS is shown in the Y-Axis of the scale.)

In document Índice de Figuras  (página 43-48)