biostatsistics

# biostatsistics

Asked by 2 years ago
5 points

“Please answer all the questions and provide rationale for the answer for each question using your own words and show your calculations to get full credit”.

1. Which of the following research question we can use case-control study to answer? [ONE POINT]

a. What is the past mortality or morbidity trends that can help estimates of the occurrence of disease in the future?

b. What is the relative frequency of the characteristic or exposure under study when you compare histories and other information from a group of cases and from a comparison group?

c. What is the possibility to analyze previous research in different places and under different circumstances to establish hypotheses based on cumulative knowledge of all known factors?

d. What is the incidence of cancer in men who have quit smoking? e. None of the above

1. In a study of a disease in which all cases that developed were ascertained, if the relative risk for the association between a factor and the disease is equal to 1.0, then: [ONE POINT]

a. There is no association between the factor and the disease b. There is either no association or a negative association between the factor and the disease c. The factor protects against development of the disease d. Either matching or randomization has been unsuccessful e. The comparison group used was unsuitable, and a valid comparison is not possible 3. In a study of a disease in which all cases that developed were ascertained, if the relative risk for the association between a factor and the disease is less than 1.0, then: [ONE POINT]

a. There is no association between the factor and the disease b. There is either no association or a negative association between the factor and the disease c. The factor protects against development of the disease d. Either matching or randomization has been unsuccessful

1. Several studies have found that approximately 95% of cases of bladder cancer are due to asbestos. This measure is an example of: [TWO POINT] a. An incidence rate b. A relative risk c. An attributable risk d. A prevalence risk

Questions 5 and 6 refer to the following information:

                        OUTCOME AFTER 10 YRS


At Beginning of Study CHD Developed CHD Did Not Develop

2,200 Healthy smokers 200 2,000

5,000 Healthy nonsmokers 130 4,870

The results of a 10-year cohort study of smoking and coronary heart disease (CHD) are shown above:

1. The incidence of CHD in smokers that can be attributed to smoking is: [ONE POINT]

2. The proportion of the total incidence of CHD in smokers that is attributable to smoking is: [ONE POINT]

3. What type of study design is considered to be the ‘gold standard’ in assessing causality? [ONE POINT]

a. Cohort b. Experimental c. Ecological d. Case-control

1. A random sample of middle age sedentary males was selected from four census tracts, and each man was examined for coronary artery disease. All those having the disease were excluded from the study. All others were randomly assigned to either an exercise group, which followed for a two-year program of systematic exercise, or to a control group, which had no exercise program. Both groups were observed semiannually for any difference in incidence of coronary heart disease.

• What type of study (study design) you would assign to this information? Why? [ONE POINT]

1. All of the following are not criteria when making causal inferences except: [ONE POINT] a. Inconsistency with existing knowledge b. Dose-response relationship c. Predictive value d. inconsistency of association in several studies

2. All of the following are measures of process of health care in a clinic except: [ONE POINT] a. Proportion of patients who have complications of a disease b. Proportion of patients in whom blood pressure is measured c. Proportion of patients whose height and weight are measured d. Proportion of patients advised to stop smoking e. Proportion of patients whose bill is reduced because of financial need

3. A major problem resulting from the lack of randomization in a cohort study is: [ONE POINT] a. The possibility that a factor that led to the exposure, rather than the exposure itself, might have caused the disease b. The possibility that a greater proportion of people in the study may have been exposed c. The possibility that a smaller proportion of people in the study may have been exposed d. That, without randomization, the study may take longer to carry out

4. It has been suggested that physicians may examine women who use oral contraceptives more often or more thoroughly than women who do not. If so, and if an association is observed between phlebitis and oral contraceptive use, the association may be due to: [ONE POINT]

a. Selection bias b. Surveillance bias c. Interviewer bias d. Recall bias

1. Residents of three villages with three different types of water supply were asked to participate in a survey to identify cholera carriers. Because several cholera deaths had occurred recently, virtually everyone present at the time underwent examination. The proportion of residents in each village who were carriers was computed and compared. What is the proper classification for this study? [ONE POINT] a. Case-control study b. Cross-sectional study c. Non-concurrent cohort study d. Experimental study

2. Colon cancer is diagnosed in 68 patients per year within a community of 10,000 unaffected individuals. A screening test is applied to all residents of this community. • What is the sensitivity (in %) of the screening test, if it detects 62 of the colon cancer patients. What is the specificity if the test correctly determines that 9,900 of the unaffected persons who do not have colon cancer? What is the positive predictive value? What is the negative predictive value [Interpret the results and show your calculations for full credit]. a. The sensitivity of the test is [ONE POINT]_____________ b. The specificity of the test is [ONE POINT] ______ c. The positive predictive value of the test is [ONE POINT] _____________ d. The negative predictive value of the test is [ONE POINT] ____________ e. What are your overall comments about the validity of this test? [ONE POINT]

Question 16 is based on the information given below:

In a case-control study of the relationship of radiation exposure and thyroid cancer, 50 cases admitted for thyroid cancer and 100 “controls” admitted during the same period for treatment of hernias were studied. Only the cases were interviewed, and 20 of the cases were found to have been exposed to x-ray therapy in the past, based on the interviews and medical records. The controls were not interviewed, but a review of their hospital records when they were admitted for hernia surgery revealed that only 2 controls had been exposed to x-ray therapy in the past. 15. Based on the description given above, what source of bias is least likely to be present in this study? [ONE POINT] a. Recall bias b. Bias due to controls being non-representative of the non-diseased population c. Bias due to use of different methods of ascertainment of exposure in cases and controls d. Bias due to loss of subjects from the control group over time e. Selection bias for exposure to x-ray therapy in the past

1. Of 3,000 persons who had received radiation treatment in childhood because of an enlarged thymus, cancer of the thyroid developed in 65 and a benign thyroid tumor developed in 125. A comparison group consisted of 5,000 children who had received no such treatment (brothers and sisters of the children who had received radiation treatment). During the follow-up period, none of the comparison group developed thyroid cancer, but benign thyroid tumors developed in 15.

Calculate the relative risk for benign thyroid tumors. Using your own words, interpret the relative risk. [TWO POINTS]

1. The extent to which a specific health care treatment, service, procedure, program, or other intervention does what it is intended to do when used in a community-dwelling population is termed its: [ONE POINT] a. Effectiveness b. Efficacy c. Effect modification d. Efficiency e. None of the above

2. The best index (indices) for concluding that an early detection program for breast cancer truly improves the natural history of disease, 10 years after its initiation, would be: [ONE POINT]

a. Improved long-term survival rates for breast cancer patients (adjusted for lead time) b. A smaller proportionate mortality for breast cancer 10 years after initiation of the early detection program compared to the proportionate mortality prior to its initiation c. A decrease in incidence of breast cancer d. None of the above

1. When a new treatment is developed that prevents death but does not produce recovery from disease, the following will occur: (ONE POINT)

a. Prevalence of the disease will decrease b. Prevalence of the disease will increase c. Incidence of the disease will increase d. Incidence of the disease will decrease e. The incidence and the prevalence of the disease will decrease

1. The extent to which a specific health care treatment, service, procedure, program, or other intervention produces a beneficial result under ideal controlled conditions is its: [ONE POINT] a. Effectiveness b. Effect modification c. Efficiency d. None of the above

2. A causal relationship between cigarette smoking and lung cancer was first suspected in the 1920s on the basis of clinical observations. To test this apparent association, numerous epidemiologic studies were undertaken between 1930 and 1960. Two studies were conducted by Richard Doll and Austin Bradford Hill in Great Britain. The first was a case-control study begun in 1947 comparing the smoking habits of lung cancer patients with the smoking habits of other patients. The second was a cohort study begun in 1951 recording causes of death among British physicians in relation to smoking habits. This case study deals with the case-control study.

Data for the case-control study were obtained from hospitalized patients in London and vicinity over a 4-year period (April 1948 – February 1952). Initially, 20 hospitals, and later more, were asked to notify the investigators of all patients admitted with a new diagnosis of lung cancer. These patients were then interviewed concerning smoking habits, as were controls selected from patients with other disorders (primarily non-malignant) who were hospitalized in the same hospitals at the same time.

The study group included 1,465 cases (1,357 males and 108 females). The following table shows the relationship between cigarette smoking and lung cancer among male cases and controls.

Table 1. Smoking status before onset of the present illness, lung cancer cases and matched controls with other diseases, 1948-1952

                                Cases                  Controls


Cigarette smoker

Non smoker

                                        1,465                1,465


a. How representative of all persons with lung cancer are hospitalized patients with lung cancer? [ONE POINT]

b. How representative of the general population without lung cancer are hospitalized patients without lung cancer? [ONE POINT]

c. Estimate the odds ratio from the data in table 1 and interpret the odds ratio. [TWO POINTS]

1. Under what circumstances would it be desirable to minimize the percentage of individuals with false negative results on a test? (ONE POINT)

2. During July 2014, a county health department received reports of 12 new cases of measles. What additional information is needed to determine whether this group of cases is an outbreak? [ONE POINT]

3. Discuss the different types of screening programs. Give example of each type. [TWO POINTS]

4. Discuss the different types of biases that can occur in a screening program. [ONE POINT]

5. In general, screening should be undertaken for diseases with the following feature(s): [ONE POINT]

a. Diseases with a low prevalence in identifiable subgroups of the population b. Diseases for which case-fatality rates are low c. Diseases that are readily diagnosed and for which treatment efficacy has been shown to be equivocal in evidence from a number of clinical trials d. Diseases with a natural history that can be altered by medical intervention

1. Data on 1075 male respondents to the 2003 Health Information National Trends Study were collected from October 2002 to April 2003 and analyzed in 2008 to examine the associations among race/ethnicity, and the perception of the risk of developing prostate cancer for African-American, Hispanic, and non-Hispanic white men aged ≥45 years without a history of prostate cancer.
• What study design is been used for this study? Why? [ONE POINT]
1. Patients were randomly assigned to the PRO-SELF intervention (n = 93) or standard care (n = 81). Patients in the standard care arm were seen by a research nurse three times and were called three times by phone between the home visits. PRO-SELF group patients were seen by specially trained intervention nurses and received a psychoeducational intervention, were taught how to use a pillbox, and were given written instructions on how to communicate with their physician about unrelieved pain and the need for changes in their analgesic prescriptions. Patients were coached during two follow-up home visits and three phone calls on how to improve their cancer pain management.
• What study design is been used for this study? Why? [ONE POINT]
1. What is justice? [ONE POINT] A) Protection from physical and psychological harm and exploitation B) Freedom to control their own actions C) Participants right to self-determination D) Right to fair treatment

2. Which can cause bias in a study? [ONE POINT] a. Participants' truthful responses b. Adequate study design c. Consistent methods of data collection d. Researcher subjectivity

3. What serves as the basis for regulations affecting research by the U.S. government? [ONE POINT]

a. The Belmont Report b. The Declaration of Helsinki c. The Nuremberg Code d. The Code of Ethics of the American Psychological Association

1. Explain the relationship between sensitivity and false negative results? Give example (TWO POINTS)

2. Which indicator answers the following question from the patients: “Given that I do not have a positive test, what is my chance that I do not have the disease?” [ONE POINT]

3. A colleague informs the epidemiologist of a new screening test for the early detection of lung cancer. How might the test be assessed before it is used by the general medical community? [ONE POINT]

4. The purpose of a double blind or double masked study is to: [ONE POINT]

a. Achieve comparability of treated and untreated subjects b. Reduce the effects of sampling variation c. Avoid subject bias and sampling variation d. Avoid observer bias and sampling variation e. Avoid observer and subject bias

1. All of the following are potential benefits of a randomized clinical trial, except: [ONE POINT]

a. The likelihood that the study groups will be comparable is increased b. Self-selection for a particular treatment is eliminated c. The external validity of the study is increased d. Assignment of the next subject cannot be predicted e. The therapy that a subject receives is not influenced by either conscious or subconscious bias of the investigator

1. The major purpose of random assignment in a clinical trial is to: [ONE POINT]

a. Reduce selection bias in the allocation of treatment b. Help ensure that study subjects are representative of the general population c. Facilitate double blinding (masking) d. Facilitate the measurement of outcome variables e. Ensure that the study groups have comparable baseline characteristics

2. Investigators conducted a retrospective cohort study to investigate outbreak gastroenteritis in California. Use the results of the following table to answer the following questions: Food Ate Did not eat Ill Well AR Ill well AR RR Salad 35 17 67.3 17 22 43.6 1.5 Potato Salad 50 12 80.6 10 35 22.2 3.0 Spinach 25 10 71.4 20 30 40.0 1.8 Chicken 15 11 57.7 16 12 57.1 1.0 Fruits 8 30 21.1 6 18 25.0 0.8

A. What is the most likely food that causes this outbreak? Why? (TWO POINTS)

biostatsistics
Ebony Bankhead

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Asked: 2 years ago