Introduction:
This report will examine the effect of garbage removal and location and plague status. Both garbage removal and location serve as risk factors and being a plague a cause is the outcome. This risk outcome association will be explored thorough various odds ratio and chi square calculations. The plague is also known as “the black death” and wiped out nearly half of the European population during the middle ages. There are three strains of the Y.pestis bacterium leading to either pneumonic plague, septicemic plague or bubonic plague. Pneumonic plague was spread via droplet transmission and had a nearly 100% case fatality rate. The bubonic plague is the subject of this study and was named as such because of the hardened lymph nodes …show more content…
This was case for assessing the association between location (risk factor) and plague cases (outcome). The Odds Ratio is found via ad/bc x 100%, where each letter represents a cell in a two by two table (Szumilas 2010). Once the OR is calculated, it needs to be tested for statistical significance by a chi square test. The chi square test will establish the significance of the OR depending on whether or not the chi square observed value exceeds the expected value. If this is the case, then the OR generated is robust and can be then assessed on whether it satisfies the OR decision rules. The OR is also provided with a confidence interval, typically 95% or 99%, which represents the range of values that the researcher is confident the OR will be found within 95% (or 99) of the time (Eqn1). The smaller the range, the more precise the OR (Szumilas 2010). This report will make use of a 99% confidence interval and will be using a Mantel-Haenszel chi square to assess OR validity. The formula to determine the MH chi square can be found in the appendix (Eqn2).
The MH Summary OR (Eqn3) will also be used to determine whether there is confounding present in the results. This OR takes into account the different strata and summates them in this ratio (Robins et al 1986). Finally, an interactive chi square will be used through the Outbreak Calculator (Sawchuk) to determine whether the stratum specific OR values are …show more content…
The next relationship that was analyzed was whether location was a risk factor for plague status, regardless of whether or not there was garbage removal. The three locations analyzed were Coastal Port City (Figure 2), Inland Rural (Figure 3) and Inland City (Figure 4). For each location the Crude OR was not significant, thus location did not increase the odds of becoming a plague case, irrespective of garbage removal. Finally, chi square analysis was done to determine the relationship of location and garbage removal. This analysis was not an odds ratio calculation since this is a purely a measure of association with no disease. For each location, there was no significant relationship with garbage removal outcome (Figure 5). Thus no area had a significant deviance in whether there was garbage removal or
This report will examine the effect of garbage removal and location and plague status. Both garbage removal and location serve as risk factors and being a plague a cause is the outcome. This risk outcome association will be explored thorough various odds ratio and chi square calculations. The plague is also known as “the black death” and wiped out nearly half of the European population during the middle ages. There are three strains of the Y.pestis bacterium leading to either pneumonic plague, septicemic plague or bubonic plague. Pneumonic plague was spread via droplet transmission and had a nearly 100% case fatality rate. The bubonic plague is the subject of this study and was named as such because of the hardened lymph nodes …show more content…
This was case for assessing the association between location (risk factor) and plague cases (outcome). The Odds Ratio is found via ad/bc x 100%, where each letter represents a cell in a two by two table (Szumilas 2010). Once the OR is calculated, it needs to be tested for statistical significance by a chi square test. The chi square test will establish the significance of the OR depending on whether or not the chi square observed value exceeds the expected value. If this is the case, then the OR generated is robust and can be then assessed on whether it satisfies the OR decision rules. The OR is also provided with a confidence interval, typically 95% or 99%, which represents the range of values that the researcher is confident the OR will be found within 95% (or 99) of the time (Eqn1). The smaller the range, the more precise the OR (Szumilas 2010). This report will make use of a 99% confidence interval and will be using a Mantel-Haenszel chi square to assess OR validity. The formula to determine the MH chi square can be found in the appendix (Eqn2).
The MH Summary OR (Eqn3) will also be used to determine whether there is confounding present in the results. This OR takes into account the different strata and summates them in this ratio (Robins et al 1986). Finally, an interactive chi square will be used through the Outbreak Calculator (Sawchuk) to determine whether the stratum specific OR values are …show more content…
The next relationship that was analyzed was whether location was a risk factor for plague status, regardless of whether or not there was garbage removal. The three locations analyzed were Coastal Port City (Figure 2), Inland Rural (Figure 3) and Inland City (Figure 4). For each location the Crude OR was not significant, thus location did not increase the odds of becoming a plague case, irrespective of garbage removal. Finally, chi square analysis was done to determine the relationship of location and garbage removal. This analysis was not an odds ratio calculation since this is a purely a measure of association with no disease. For each location, there was no significant relationship with garbage removal outcome (Figure 5). Thus no area had a significant deviance in whether there was garbage removal or