NUR627 Advanced Epidemiology and Biostatistics for Nursing Sample Assignment

NUR 627: Advanced Epidemiology and Biostatistics for Nursing

Assignment 1

The test includes 40 questions for a total of 50 points. (20% of the Assignment grade)

“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 is a case-control study? [ONE POINT]

1. Assignment of past mortality or morbidity trends to permit estimates of the occurrence of disease in the future -cohort study
2. Assignment of the incidence of cancer in men who have quit smoking-follow up study
3. Analysis of previous research in different places and under different circumstances to permit the establishment of hypotheses based on cumulative knowledge of all known factors-cross sectional study
4. Obtaining histories and other information from a group of known cases and from a comparison group to determine the relative frequency of a characteristic or exposure under study
   
5. Both a and c

this is case control study because we are dealing with known cases which makes the study a case controlled study

2. 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]

1. There is no association between the factor and the disease
2. There is either no association or a negative association between the factor and the disease
3. The factor protects against development of the disease
4. Either matching or randomization has been unsuccessful
5. The comparison group used was unsuitable, and a valid comparison is not possible

If the relative risk for association between a factor and the disease is 1, it means the factor is not a risk for the disease.

3. 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]

The study design suitable for this information is randomized controlled trial because we can estimate relative risk, incidence and we can also measure any impact- Randomized Clinical Trial

Questions 4 and 5 refer to the following information:

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

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

Attributable risk = incidence rate in the exposed – incidence rate in the nonexposed

Incidence rate among smokers =190 cases/2,000 population at risk x1,000= 95 per 1,000

Incidence rate among nonsmokers=35 cases /4,000 population at risk x1,000=8.75 or 9 per 1,000

95-8.75=86.25 or 86 cases of CHD per 1,000 population incidence of CHD in smokers that can be attributed to smoking.

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

The proportion of the incidence in the total population = (( incidence in exposed group – incidence in nonexposed group)/incidence in exposed group )x 100

Incidence rate among smokers = 190 cases/2,000 population at risk x 1000= 95 per 1,000

Incidence rate among nonsmokers = 35 cases/4,000 population at risk x 1000 = 8.75 or 9 per 1,000

190/2000-35/4000

/190/2000*100= 0.095-0.00875/ 0.095*100= 90.78% the proportion of the total incidence of CHD in smokers that is attributed to smoking

6. All of the following are important criteria when making causal inferences except: [ONE POINT]

1. Consistency with existing knowledge
2. Dose-response relationship
3. Predictive value
4. Consistency of association in several studies
5. Strength of association

Predictive value is not important when making casual inferences because in casual inferences we are concluding about the conditions of occurrence of an effect.

7. All of the following are measures of process of health care in a clinic except: [ONE POINT]

1. Proportion of patients in whom blood pressure is measured
2. Proportion of patients advised to stop smoking
3. Proportion of patients whose height and weight are measured
4. Proportion of patients who have complications of a disease
5. Proportion of patients whose bill is reduced because of financial need

Proportion is to adjust or regulate (something) so that it has a particular or suitable relationship to something else

8. Colon cancer is diagnosed in 55 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 48 of the colon cancer patients. What is the specificity if the test correctly determines that 9,650 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].

1. The sensitivity of the test is 48/55 = 0.87 x 100 = 87%, patient who were positive results have colon cancer
2. The specificity of the test is 9650/9945 = 0.97

97% of people who tested negative didn’t have cancer.

PPV = 48/343 = 0.139

NPV = 9650/9657 = 0.999

So, 13.9% of the probability that people who were screened with a positive screen of colon cancer was diagnosed with colon cancer and 99.9% the probability that people who were screened with a negative screen of colon cancer and they don’t have colon cancer

1. What are your overall comments about the validity of this test? [ONE POINT]

Going by the sensitivity, specificity, positive predictive and negative predictive values, we see that it has a good validity.

9. Which of the following is not an advantage of a prospective cohort study? [ONE POINT]

1. Precise measurement of exposure is possible
2. Incidence rates can be calculated
3. It usually costs less than a case-control study
4. Recall bias is minimized compared with a case-control study
5. Many disease outcomes can be studied simultaneously

this is not the advantage of a prospective cohort study because the prospective cohort study costs more than a case control study.

10. A major problem resulting from the lack of randomization in a cohort study is: [ONE POINT]

1. The possibility that a greater proportion of people in the study may have been exposed
2. The possibility that a smaller proportion of people in the study may have been exposed
3. The possibility that a factor that led to the exposure, rather than the exposure itself, might have caused the disease
4. That, without randomization, the study may take longer to carry out
5. Planned crossover is more likely

If we observe an association of an exposure with a disease, we are left with uncertainty as to whether the association may be a result of the fact that people were not randomized to the exposure, or whether it was factors that led people to be exposed, that are associated with the disease

11. Which of the following is an approach to handling confounding? [ONE POINT]

1. Individual matching
2. Stratification
3. Group matching
4. Adjustment
5. All of the above

We can approach to handling confounding by individual matching, stratification, group matching and adjustment, so the correct option is all of the above because all the equations are satisfied for handling confounding

12. 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]

1. Selection bias
2. Interviewer bias
3. Nonresponse bias
4. Recall bias
5. Surveillance bias

Surveillance bias what some texts call detection bias, occurs when one group is followed more closely than the other group. This could lead to an outcome being diagnosed more often in the more closely followed group, but not because it truly occurred more often in that group

13. 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]

1. Case-control study
2. Concurrent cohort study
3. Non-concurrent cohort study
4. Cross-sectional study
5. Experimental study

this is cross sectional study because the sample was collected from three different villages, then the data is studied to compute and compare the result for three villages

Question 14 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.

14. Based on the description given above, what source of bias is least likely to be present in this study? [ONE POINT]

1. Recall bias
2. Bias due to loss of subjects from the control group over time
3. Bias due to controls being non-representative of the non-diseased population
4. Bias due to use of different methods of ascertainment of exposure in cases and controls
5. Selection bias for exposure to x-ray therapy in the past

Bias can occur when study cohorts have unequal losses to follow-up.

15. Of 2,000 persons who had received radiation treatment in childhood because of an enlarged thymus, cancer of the thyroid developed in 30 and a benign thyroid tumor developed in 70. A comparison group consisted of 6,000 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. [ONE POINT]

Relative Risk = (70/2000) / (15/6000) = 0.035/0.0025 = 14

Persons who had received radiation treatment would be 14 times as likely as those with no such treatment to develop benign thyroid.

16. 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]

1. Effectiveness
2. Effect modification
3. Efficiency
4. Efficacy
5. None of the above

Effectiveness is the ability of an intervention to have a meaningful effect on patients in normal clinical conditions. Clinical trial measuring effectiveness are also called pragmatic trials or phase III or IV clinical trials. Effectiveness studies (also known as pragmatic studies) examine interventions under circumstances that more closely approach real-world practice, with more heterogeneous patient populations, less-standardized treatment protocols, and delivery in routine clinical settings.

17. The best index (indices) for concluding that an early detection program for breast cancer truly improves the natural history of disease, 20 years after its initiation, would be: [ONE POINT]

1. 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
2. A decrease in incidence of breast cancer
3. A decrease in the prevalence of breast cancer
4. Improved long-term survival rates for breast cancer patients (adjusted for lead time)
5. None of the above

It is the best indices for concluding that an early detection program for breast cancer improves the natural history of disease 20 years after its initiation.

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

1. Diseases with a low prevalence in identifiable subgroups of the population
2. Diseases with a natural history that can be altered by medical intervention
3. Diseases for which case-fatality rates are low
4. Diseases that are readily diagnosed and for which treatment efficacy has been shown to be equivocal in evidence from a number of clinical trials
5. None of the above

Epidemiological screening is to determine the risk factors associated with disease and to find out the factors tat may protect the people from disease. These studies cannot prove a specific risk factor that actually causes disease. In contrast, the epidemiological evidence shows that certain risk factors are associated with a higher incidence of disease in population.

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

1. Prevalence of the disease will decrease
2. Prevalence of the disease will increase
3. Incidence of the disease will decrease
4. The incidence and the prevalence of the disease will decrease
5. Incidence of the disease will increase

Since the treatment is only preventing the deaths, but it is not good to control the prevalence of disease or it is not good in recovering from the diseases. This will increase the number of patients which means that the prevalence of disease will increase

20. 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]

1. Effectiveness
2. Efficacy
3. Efficiency
4. Effect modification
5. None of the above

Efficacy is the ability to provide a beneficial effect. In healthcare, efficacy of a product to yield therapeutic benefits is explored.

21. During August 2017, LA county health department received reports of 10 new cases of hepatitis A. What additional information is needed to determine whether this group of cases is an outbreak? [ONE POINT]

We need the median and total number of cases to determine whether this group of cases is an outbreak. Surveillance records are utilized from department of health, hospital records, registries, mortality statistics, national data, etc. and a survey can be conducted to figure out the background of the disease in the county.

22. What are the different types of screening programs? Give example of each type. [ONE POINT]

Unrecognized symptomatic disease screening: what IS making the person sick?

Ex. Iron deficiency

Disease screening: what WILL make the person sick?

Ex. mammogram

Risk factor screening: what MIGHT make the person sick

Ex. Smoking as risk factor for lung cancer

Mass screening: screen a whole population

Ex. X-rays for TB

Multiple or multiphasic screening: use variety of screening tests on the same occasion

Ex. Annual health check up

Targeted screening: screen groups with specific exposures, used in environmental and occupational health

Ex. Battery workers

Case finding screening: patients who consult a medical practitioner for another purpose

Ex. Checking of blood pressure of patients coming in for flu shots

23. What are the different types of biases that can occur in a screening program? [ONE POINT]

There are two common types of biases

Information bias - data is not accurate, possibly due to faulty instruments, or possibly the data is wrong.

Selection bias - the study population is not representative of the larger population, possibly because of a poor sampling process, or because of a lot of individuals are lost to follow-up

Common biases in screening include:

Lead time (information bias)- the systematic error of apparent increased survival from detecting disease in an early stage

Length (information bias) - the systematic error from detecting disease with a long latency or pre-clinical period

Referral/Volunteer bias (selection bias) - the systematic error from detecting disease in persons who have a propensity to seek health care

Detection (information bias) - the detection of insignificant disease

Over diagnosis Bias: there is a false increase in rates of detection and diagnosis due to the screening because the individuals conducting the screening have so much enthusiasm for the program

24. Data on 2000 male respondents to the 2003 Health Information National Trends

Assignment 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]

Case control study

This is case control study because we have control the time period and the ethnicity group to complete the study

Cross sectional study

25. What is justice? [ONE POINT]

1. Freedom to control their own actions
2. Protection from physical and psychological harm and exploitation
3. Participants right to self-determination
4. Right to fair treatment

Justice includes the right to fair treatment and the right to privacy.

26. Which can cause bias in a study? [ONE POINT]

1. Researcher subjectivity
2. Participants' truthful responses
3. Consistent methods of data collection
4. Adequate study design

Experimenter bias is a process where the researcher performing the research can influence the results in order to portray a certain outcome.

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

1. The Nuremberg Code
2. The Declaration of Helsinki
3. The Code of Ethics of the American Psychological Association
4. The Belmont Report

The Belmont report provides ethical principles and guidelines for protection of human subject of research. The Nuremberg Code 10 codes for guidelines for experiments. The Declaration of Helsinki is a set of ethical principle regarding human experimentation developed for medical community by the World Medical Association. While The Code of Ethics of the American Psychological Association applies only to psychologists’ activities that are part of their scientific, educational or professional role as psychologist.

28. Explain the relationship between sensitivity and false negative results?

Give example (ONE POINT)

Specificity is the ability to correctly identify the risk of developing prostate cancer in a person whereas false positive is the ability to incorrectly identify the risk of developing prostate cancer in a person. For example, if we identify a person without risk of prostate cancer as low risk or negligible risk, then this specificity. If we identify a person with risk of prostate cancer as a risk free person, then this is false positive

Inversely proportional

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

When the disease under test is spreadable and progresses quickly, then it is desirable to minimize the percentage of individuals with false negative

30. Which indicator answers the following question from the patients: “Given that I have a positive test, what is my chance that I have the disease?” [ONE POINT]

Positive predicative value which states the probability that a person with a positive result will have or has the disease

31. 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]

It can be assessed using the sensitivity, specificity and predictive values for a pilot sample and based on the same it can be extended to general medical community.

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

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

All of the following are potential benefits of randomized clinical trial except the external validity of the study is increased

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

1. Help ensure that study subjects are representative of the general population
2. Facilitate double blinding (masking)
3. Reduce selection bias in the allocation of treatment
4. Ensure that the study groups have comparable baseline characteristics
5. Facilitate the measurement of outcome variables

The goal of randomization is to eliminate the possibility that the investigator will know what the assignment of the next patient will be, because such knowledge introduces the possibility of bias on the part of the investigator regarding the treatment group to which each participant will be assigned.

34. Investigators conducted a retrospective cohort study to investigate outbreak of Hepatitis A in San Diego. Use the results of the following table to answer the following questions:

A. Complete the following:

1. Attack rate (AR) for those who ate the specific identified food and those who did not eat these food [ONE POINT]

See Table

1. The relative risk (RR) for each specific identified food [ONE POINT]

See Table

1. Which food is the most likely cause of the outbreak? Why? [ONE POINT]

Potato Salad is most likely the cause of outbreak because it has the maximum value of RR as compared to the other foods.

And Chicken

1. What steps you will take after the identification of the source of outbreak? [ONE POINT]

We should implement control measures and do preventive measures such as Destroying Contaminated foods and Make sure of clean meal preparation.

35. Researchers select 200 patients with colon cancer and 200 patients without colon cancer. Of the 200 patients with colon cancer, 45 smoke cigars while 15 of the 200 patients without colon cancer smoke cigars. -Case Control Assignment

1. Calculate a measure of association between colon cancer and cigar smoking. Show your work. [ONE POINT]

Odds ratio: 45 x 185/ 15 x 155 = 8325/2325= 3.58

1. Interpret the measure of association you calculated. [ONE POINT]

A risk ratio of more than 1 suggests an increased risk of that outcome in the exposed group therefore, smokers have an increased risk of incidence of colon cancer compared to patients who did not smoke.

Odds ratio is another measure of association that quantifies the relationship between an exposure with 2 categories and a health outcome. It is sometimes called the cross product ratio. The odds ratio of 3.58 and RR of 3 reflect a very strong association between patients who smoke and patient who do not smoke in the occurrence of Colon CA. It shows that subjects who smoked are 3.58 times the risk of colon cancer compared to subjects who did not smoke.

36. To study the relationship between oral contraceptive use and ovarian cancer, CDC initiated a case-control study – the Cancer and Steroid Hormone Assignment. Case-patients were enrolled through eight regional cancer registries participating in the Surveillance, Epidemiology, and End Results (SEER) program of the National Cancer Institute.

1. What types of bias are of particular concern in this study? [ONE POINT]

Confounding, Information Bias, Selection Bias- Ascertainment bias of disease status and Interviewer Bias

Selection and recall bias

1. What steps might you take to minimize these potential biases in this study? [ONE POINT]

Enrolling all women with cases of newly diagnosed, histological confirmed, primary ovarian cancer who resided in one of eight geographic areas covered by cancer registries. Controls are randomly selected using numbers from same geographic areas.

CDC investigators conducted group sessions to train interviewers in the administration of pretested standard questionnaire. Same interviewers and questionnaires were used for control and cases. Neither cases nor controls were told of the specific a priori hypotheses to be tested by the study. Recall bias of oral contraceptive exposure was minimized by showing participants a book with photographs of all OC preparations ever marketed in the United States and by using a calendar to relate contraceptive and reproductive histories to other life events.

1. Under what circumstances would age be a confounder in this study? [ONE POINT]

In many epidemiologic studies, age is a confounding factor. Cofounding is the misinterpretation of association between disease and its exposure. Age can be a confounder in this study if the age is associated with the exposure to disease and with the outcome which is ovarian cancer. Age was related both to OC use and to case-control status

1. The primary purpose of this study was to measure and test the association between OC use and ovarian cancer. The distribution of exposure to OCs among cases and controls is shown in Table 2 below. From these data in table 2, can you calculate the risk of ovarian cancer among oral contraceptive users? Provide rationale. [ONE POINT]

Table 2. Ever-use of oral contraceptives among ovarian cancer cases and controls,

We can calculate the risk of ovarian cancer among oral contraceptive using odds ratio to estimate the measure of association in relation to ovarian cancer. Since this is a case control study, we cannot directly calculate risk ratio, it is because we do not have the data for the denominator. The data on b and d cells represent the control group. The odds ratio is not a good approximation of risk ratio when the disease under study is not rare.

OR= ad/bc

OR=99*683/959*80=67,617/76,720=0.88

No, you cannot calculate the risk. This is a case control study. We are measuring retrospectively the exposure.

37. What is effect modification? How do you look for effect modification in a study? [ONE POINT]

When the odd ratio is different among different groups, then we say it effect modification. We can look for the effect modification by checking the variable rate, i.e. the rate can be positive or negative. The variable rate can affect the observed risk factor of exposure to a disease.

For example, if the variable rate is positive, it can lead different age groups to have unequal odds ratio.

38. The figures (1, 2, and 3) below represented the epidemiologic curve for outbreak investigation. Discuss the type of source of the epidemic for each figure (TWO POINTS).

1. First figure shows common point source because it has gradual downward slope and sharp upward slopes
2. Second figure shows common persistent source because in this the people are exposed continuously to common source which is also harmful to them
3. Third figure shows propagated source because it shows that the diseases is spreading from one person to other persons.

39. Fill in the spaces: [ONE POINT]

The mean (X ) is a measure of Central Tendency of a distribution while the standard deviation (SD) is a measure of dispersion of its scores. Both X and SD are descriptive statistics

40. The following list represents the number of nursing students enrolled in a particular nursing program between the years of 2001 and 2007, respectively:

520, 563,610, 520, 573, 639, and 599.

Calculate the mean, median, and mode of the number of the nursing students enrolled in the above program between 2001 and 2007. Show your calculations. [ONE POINT]

Mean=520+563+610+520+573+639+599/7=574.86 or 575, which is the number of the sum of all the numbers divided by how many numbers are added.

Median=520, 520, 563, 573, 599, 610, 639=573, when numbers are arranged in order and the median is the middle number.

Mode= 520, 520, 563, 573, 599, 610, 639= 520, is the most frequent occurring number.