A Review and Comparison of Methods for Detecting Outliers in Univariate Data Sets

Most real-world data sets contain outliers that have unusually large or small values when compared with others in the data set. Outliers may cause a negative effect on data analyses, such as ANOVA and regression, based on distribution assumptions, or may provide useful information about data when we look into an unusual response to a given study. Thus, outlier detection is an important part of data analysis in the above two cases. Several outlier labeling methods have been developed. Some methods are sensitive to extreme values, like the SD method, and others are resistant to extreme values, like Tukey's method. Although these methods are quite powerful with large normal data, it may be problematic to apply them to non-normal data or small sample sizes without knowledge of their characteristics in these circumstances. This is because each labeling method has different measures to detect outliers, and expected outlier percentages change differently according to the sample size or distribution type of the data. Many kinds of data regarding public health are often skewed, usually to the right, and lognormal distributions can often be applied to such skewed data, for instance, surgical procedure times, blood pressure, and assessment of toxic compounds in environmental analysis. This paper reviews and compares several common and less common outlier labeling methods and presents information that shows how the percent of outliers changes in each method according to the skewness and sample size of lognormal distributions through simulations and application to real data sets. These results may help establish guidelines for the choice of outlier detection methods in skewed data, which are often sen in the public health field

Prevention of recurrent urinary tract infections by intravesical administration of heparin: a pilot study

Objective: To assess the effect of bladder instillations using heparin on the rate of urinary tract infections in women resistant to standard therapy. Patients and methods: The medical records of all women who received bladder instillations between May 2009 and January of 2010 at the University of Wisconsin urogynecology clinic were reviewed. Eighteen women (mean age 67 years) with a history of recurrent urinary tract infections received intravesical instillations (heparin 40,000 U, 2% lidocaine 8 ml, sodium bicarbonate 4 ml) once weekly for 6 weeks. Patients were considered resistant to standard therapy if their condition failed to respond to chronic suppression antibiotic therapy; they had chronic infections and for this reason could not be placed on chronic suppression; or they were not candidates for chronic suppression due to drug allergies. The number of urinary tract infections was monitored during treatment and for 6 months after therapy. The urinary tract infection rates were compared with the rates of urinary tract infection in the 6 months before treatment. Results: Seventy-eight percent of patients responded to therapy. Subjects were thought to have responded to therapy if there was a greater than 50% reduction in the rate of urinary tract infection. Other variables reviewed included evidence of chronic infection, hormonal status, glomerular filtration rate, age, body mass index, antibiotic allergies, diabetes, hypertension, and chronic antibiotic therapy during bladder instillations. None of these variables were found to be statistically significant. Conclusion: Bladder instillations decreased the rate of urinary tract infection in this pilot study; this effect persisted into the post-treatment period. More research is needed to confirm these preliminary findings

Radiation-related occupational cancer and its recognition criteria in South Korea

Abstract Ionizing radiation is a well-known carcinogen, and is listed as one carcinogenic agent of occupational cancer. Given the increase in the number of workers exposed to radiation, as well as the increase in concern regarding occupational cancer, the number of radiation-related occupational cancer claims is expected to increase. Unlike exposure assessment of other carcinogenic agents in the workplace, such as asbestos and benzene, radiation exposure is usually assessed on an individual basis with personal dosimeters, which makes it feasible to assess whether a worker’s cancer occurrence is associated with their individual exposure. However, given the absence of a threshold dose for cancer initiation, it remains difficult to identify radiation exposure as the root cause of occupational cancer. Moreover, the association between cancer and radiation exposure in the workplace has not been clearly established due to a lack of scientific evidence. Therefore, criteria for the recognition of radiation-related occupational cancer should be carefully reviewed and updated with new scientific evidence and social consensus. The current criteria in Korea are valid in terms of eligible radiogenic cancer sites, adequate latent period, assessment of radiation exposure, and probability of causation. However, reducing uncertainty with respect to the determination of causation between exposure and cancer and developing more specific criteria that considers mixed exposure to radiation and other carcinogenic agents remains an important open question

Factors associated with the risk perception and purchase decisions of Fukushima-related food in South Korea

<div><p>Following the Fukushima nuclear power plant accident, the risk level perceived by Koreans on the radioactive contamination of Japanese food that is being distributed in Korea remains high. Many of these perceptions are based on subjective risk perception rather than an objective measure with scientific evidence, which makes communicating risks more difficult; therefore, it is critical to understand factors associated with risk perception for effective risk communication. In this study, we identified variables that are associated with buying tendencies and opinions about the regulatory policy of Japanese seafood after the accident. A survey was conducted with 1045 adults aged over 20 years in Korea. The majority (68.8%) responded that they would not purchase Japanese seafood when radioactivity levels in the food were non-detectable. Moreover, 82.2% responded that the current levels of import restrictions on Japanese seafood must be maintained. Despite many concerns regarding the exposure to radiation and the effects from food products following the Fukushima accident, the opportunities to encounter and to collect correct information remain limited and average radioactive knowledge scores were low (3.63 out of 9). Of the various characteristics associated with purchase decisions and agreement on the current import restraints of Japanese seafood, trust levels in the government and the mass media for providing information on radioactivity were major factors that influenced risk perception. While the scope of this study was limited to seafood, it is very closely tied to daily lives, where we revealed differences about risk perceptions and agreement on import restraints of Japanese seafood per a complex mixture of individual characteristics and the surrounding environment. These results provide useful information to understand the risk perception of the potential radioactive contamination of food and to predict the public’s responses to food consumption and import restraint policies due to nuclear accidents in neighboring countries.</p></div

Factors associated with agreement with the current import restraints of Japanese seafood.

<p>Factors associated with agreement with the current import restraints of Japanese seafood.</p

Radiation knowledge and confidence in the governments’ food management.

<p>Radiation knowledge and confidence in the governments’ food management.</p

Changes in the agreement level with the maintenance of current import restraints of Japanese seafood per radiation knowledge score, the level of confidence in the information provided by the Japanese and the level of confidence in the information provided by the mass media.

<p>The x-axis denotes radiation knowledge score (A), level of confidence in the information provided by the Japanese government (B), concerns with the news bulletins (C), and the level of confidence in the information provided by the mass media (D). The y-axis shows estimates on the level of agreement of maintaining the current import restraints of Japanese seafood after adjusting for significant variables in the multivariate model. The 95% confidence interval on the estimates is shown in blue shading. Higher radiation knowledge scores and concerns with news bulletins were associated with increased agreement with maintaining the current import restraints of Japanese seafood (A, C), and higher levels of confidence in the Japanese government and the mass media were associated with the decreased agreement with maintaining the current import restraint levels on Japanese seafood (B, D).</p

Participants’ channels of information acquisition and perceptions on radiation.

<p>Participants’ channels of information acquisition and perceptions on radiation.</p

Factors associated with the decrease in seafood purchase frequencies after the Fukushima nuclear power plant accident.

<p>Factors associated with the decrease in seafood purchase frequencies after the Fukushima nuclear power plant accident.</p