Using Microsoft Excel 2010 On The Heart Disease Mortality Data Rates Versus The Total Hardness
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Microsoft Excel 2010 was used to create a scatter plot of the heart disease mortality data rates versus the total hardness of WTPs listed in Table 2.3.1. A linear regression using Microsoft Excel Data Analysis Package, 2010 was used to find the correlation along with the R2 value and adjusted R2 value. The R2 values represent the percent of the variance of the data explained by the fitted line. In this case, the R2 values represent the variance in heart disease rates that can be explained by the change in drinking water hardness. The adjusted R2 value is dependent on the number of points within the data. The significance of the R2 value was determined by the resulting p-values. The test was considered significant if the p-value was less than 0.05. WTPs were further divided by levels of hardness into moderately hard, hard, and very hard classifications to check for correlations within classifications. Linear regressions were then run on each classification. The entire statistical analysis is shown in the Appendix.
The range of water hardness of the 31 WTPs varied from 93 mg/l to 448 mg/l of total hardness with an average value of 180 mg/l. Of the 31 plants 17 had a total hardness between 120mg/l and 160mg/l, accounting for 58% of the study area.
The total population heart disease mortality rate versus water hardness was first analyzed and a positive correlation of 0.427 was obtained. The R2 value was found to be 0.183 indicating that 18.3% of