# concentration of chlorhexidine

##### Description
1. The table shows the concentration of chlorhexidine (mg) in 15 1-mL samples that have been removed from a stock solution (5 L) and assayed by ultraviolet spectroscopy. Calculate the 95% confidence interval of the population mean.
1. A clinical trial (n = 35 patients) has been performed in which the volume of distribution of a new anti-diabetes drug has been calculated as 10.2 ± 1.9 L. Calculate the 95% and 99% confidence limits of the mean value (assuming that the data originated from a normal distribution).
1. Consider the distribution of hemoglobin levels for the population of children under 6 who have been exposed to high levels of lead. Suppose that this distribution has σ = 0.85g/100ml. Because children who have lead poisoning tend to have much lower levels of hemoglobin than children who do not, we are interested in an upper confidence limit for µ (the mean of the hemoglobin levels in this population). Suppose that we have a random sample of 74 children from this population. The sample mean x = 10.6g/100ml. Estimate a 90% upper confidence limit.
1. A healthcare company that specializes in the sterile packaging of disposable gloves has decided to perform a quality audit of the resistance of a batch of packaged disposable gloves to the ingress of unsterile air. Out of a batch of 2500 packages, 200 were removed and their sterility examined using the British Pharmacopoeia sterility tests. The results showed that 35 packages failed the sterility tests. On the basis of these observations, calculate the 95% confidence limits for the proportion of defective gloves in the batch (population).
1. If 3 out of 10 mammalian cell cultures exposed to ultraviolet (UV) radiation developed chromosomal abnormalities while 9 out of 10 mammalian cell cultures developed chromosomal abnormalities when exposed to UV radiation plus a common NSAID (nonsteroidal anti-inflammatory drug).
1. a)What type of study design?
2. b)Which parameter can determine? Calculate it.
3. c)Explain the results.
1. A study was carried out in Taiwan: a total of 128 histologically or cytologically confirmed cases of hepatocellular carcinoma and 384 controls without the disease were included in the study. Of the cases, 77% were carriers of the hepatitis B surface antigen (HbsAg) compared with only 28% of the controls (Chuang et al., 1992).
2. a)Formulate a possible hypothesis question
3. b)What type of study design?
4. c)Which parament can determine? Calculate it.
5. d)Explain the results
1. Serum Carotenoids and Risk of Cervical Intraepithelial Neoplasia in Southwestern American Indian Women (Melissa A. Schiff, Ruth E. Patterson, Richard N. Baumgartner, Mary Masuk, Linda van Asselt-King, Cosette M. Wheeler and Thomas M. Becker, Published November 2001, Cancer Epidemiology, Biomarkers & Prevention )

Abstract: «The objective of this research was to evaluate the association between serum carotenoids and cervical intraepithelial neoplasia (CIN) among Southwestern American Indian women. Cases were American Indian women with biopsy-proven CIN II/III cervical lesions (n = 81) diagnosed between November 1994 and October 1997. Controls were American Indian women from the same clinics with normal cervical epithelium (n = 160). All of the subjects underwent interviews and laboratory evaluations. Interviews evaluated demographic information, sexual history, and cigarette smoking. Serum concentrations of α-carotene, β-carotene, β-cryptoxanthin, lycopene, and lutein/zeaxanthin were measured by high performance liquid chromatography. Cervical human papillomavirus infection was detected using a PCR-based test. Increasing levels of α-carotene, β-cryptoxanthin, and lutein/zeaxanthin were associated with decreasing risk of CIN II/III. In addition, the highest tertiles of β-cryptoxanthin (odds ratio = 0.39, 95% confidence interval = 0.17–0.91) and lutein/zeaxanthin (odds ratio = 0.40, 95% confidence interval = 0.17–0.95) were associated with the lowest risk of CIN. In conclusion, specially targeted intervention efforts to increase consumption of fruits and vegetables may protect Southwestern American Indian women from developing CIN».

1. a)Estimate the selection criteria for cases
2. b)Explain the results of the study using odds ratios
3. c)Determine the exposure and outcome
1. Which of the following health outcomes could be studied using a cross-sectional study design? Choose all that apply.
2. a)The prevalence of diabetes among adults in the United States in 2014
3. b)The prevalence of diabetes among all patients seen at a particular health clinic on one day in 2014
4. c)The number of new cases of diabetes diagnosed among at risk adults in the United States in 2014
5. d)The number of people in a population with diabetes who are obese and the number of people in a population with diabetes who are not obese, in the United States in 2014
1. A random sample of 1141 men and 1212 women aged 25-64 y (response rate 76%) completed a questionnaire and underwent a short examination in a clinic. Intake of beer, wine and spirits during a typical week, frequency of drinking, and a number of other factors were measured by a questionnaire. The present analyses are based on 891 men and 1098 women who were either nondrinkers or ‘exclusive’ beer drinkers (they did not drink any wine or spirits in a typical week). 500 men are beer drinkers and 325 men from this group have the obesity. 80 non-drinkers men are obese.
2. a)What type of study design?
3. b)Which parameters can be calculated?
4. c)Determine it and explain the results.
1. A randomized controlled trial is conducted to evaluate the incidence of diarrhea in 300 children with otitis media treated with a broad-spectrum antibiotic, amoxicillin + clavulanic acid, compared to amoxicillin. During the study, the participants and the investigator were not aware of the treatment allocation between experimental and control groups.

This study is:

1. Open-label
2. Single-blinded
3. Double-blinded
4. Non-blinded

The study design described above reduces:

2. Degree of bias
3. Compliance to the study protocol
4. Drop-out rate of participants
5. Duration of the study

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