1.
All of the following are true of odds ratio except:
Correct Answer
D. It is the ratio of incidence in exposed divided by incidence in nonexposed
Explanation
The odds ratio is not an estimate of relative risk, as stated in the first option. The odds ratio is a measure of association between exposure and outcome in a casecontrol study, and it can be calculated without data on rates. However, it is not the ratio of incidence in exposed divided by incidence in nonexposed. The odds ratio compares the odds of exposure in cases to the odds of exposure in controls. It tends to be biased towards 1 at high rates of disease because as the disease becomes more common, the odds ratio becomes a less accurate estimate of the relative risk.
2.
In a well designed clinical trial of treatment of ovarian cancer, remission rate at one year is similar for a new drug and usual care, The Pvalue is 0.4. This means that
Correct Answer
E. It is not possible to decide on whether one treatment is better than the other using this information alone
Explanation
The Pvalue of 0.4 indicates that there is a 40% chance of observing the results of the study if the null hypothesis (no difference between the new drug and usual care) is true. This means that the results are not statistically significant, and therefore, it is not possible to conclude that one treatment is better than the other based on this information alone.
3.
A study was made of a clinician's ability to diagnose streptococcal throat infections in 149 patients coming to the emergency department in a certain hospital. The doctor's clinical impressions were compared to the results of throat cultures or group A streptococcus. 37 patients had positive throat cultures and 27 of these were diagnosed by the doctor as having strep throat. 112 patients had negative cultures, and the doctors diagnosed 35 of these as having strep throat. The specificity of the doctors' clinical judgment was:
Correct Answer
B. 77/112
Explanation
The specificity of the doctors' clinical judgment is calculated by dividing the number of true negatives (patients with negative cultures correctly diagnosed as not having strep throat) by the total number of patients with negative cultures. In this case, there were 112 patients with negative cultures and the doctors correctly diagnosed 77 of them as not having strep throat. Therefore, the specificity is 77/112.
4.
From the study in Question 3, the predictive value of the doctors' clinical judgment for streptococcal sore throat was:
Correct Answer
C. 27/62
Explanation
The study in Question 3 found that the predictive value of the doctors' clinical judgment for streptococcal sore throat was 27/62. This means that out of the total number of cases evaluated by the doctors, 27 were correctly diagnosed as streptococcal sore throat while 35 were incorrectly diagnosed. Therefore, the doctors' clinical judgment had a success rate of 27 out of 62 cases.
5.
The mode of transport of an infectious agent through the environment to a susceptible host is called a:
Correct Answer
D. Vehicle
Explanation
A vehicle is a mode of transport that carries an infectious agent through the environment to a susceptible host. This can include objects, such as contaminated food or water, that act as intermediaries in transmitting the infectious agent. Unlike carriers, which are individuals who harbor and spread the infectious agent without showing symptoms, a vehicle does not necessarily involve a living organism. A reservoir refers to the natural habitat where the infectious agent lives and multiplies, while a vector is an organism, such as a mosquito, that transmits the infectious agent.
6.
A longitudinal or prospective study is also referred to as a(n)
Correct Answer
C. Cohort study
Explanation
A cohort study is a type of longitudinal or prospective study where a group of individuals with a common characteristic or exposure are followed over a period of time to observe the development of specific outcomes. This type of study design allows researchers to investigate the causeandeffect relationship between the exposure and the outcome. Therefore, the correct answer for this question is cohort study.
7.
The following drug trial is synonymous with the term "clinical trial"?
Correct Answer
B. Full scale Evaluation of Treatment
Explanation
The term "clinical trial" refers to a research study conducted on humans to evaluate the safety and effectiveness of a medical intervention, such as a drug. "Full scale Evaluation of Treatment" accurately describes this process, as it involves a comprehensive assessment of the treatment's efficacy and potential side effects in a larger population. The other options, such as "Clinical pharmacology and toxicity" and "Initial Clinical Investigation for Treatment Effect," may be related to aspects of the drug trial but do not encompass the entire process. "Post marketing Surveillance" refers to monitoring the drug's safety and effectiveness after it has been approved and is being used by the general public.
8.
When designing a study to determine whether there is a direct association between a particular exposure and an outcome, one should anticipate that potential alternative explanation(s) may exist. Which of the following is a way to deal with confounding?
Correct Answer
B. Randomization
Explanation
Randomization is a way to deal with confounding in a study. It involves randomly assigning participants to different groups, such as an exposed group and an unexposed group. This helps to ensure that any potential confounding factors are distributed equally among the groups, reducing the likelihood of bias. By randomly assigning participants, the study design can help control for potential alternative explanations and increase the validity of the results.
9.
Cedar Rivers is a community of 100,000 persons in central Iowa. During the year of the floods (2008), there were 1,000 deaths from all causes. A study of all cases of tuberculosis found the number of deaths at 300 (200 males and 100 females). During 2007, there were only 60 deaths from tuberculosis, 50 of them males. The crude mortality rate for Cedar Rivers in 2008 was:
Correct Answer
C. 10 per 1,000
Explanation
The crude mortality rate for Cedar Rivers in 2008 was 10 per 1,000. This is calculated by dividing the number of deaths (1,000) by the population size (100,000) and then multiplying by 1,000 to express it per 1,000 population. The information about tuberculosis deaths in 2007 and 2008 is not relevant to calculating the crude mortality rate.
10.
A screening test for brain cancer was administered to 400 women with biopsyproven brain cancer and to 400 women without brain cancer. The test results were positive for 100 of the proven cases and 50 of the normal women. The predictive value of a positive test is
Correct Answer
D. 67%
Explanation
The predictive value of a positive test is 67% because it is calculated by dividing the number of true positive results (100) by the sum of true positive and false positive results (100 + 50). This gives us a fraction of 100/150, which simplifies to 2/3 or 0.67 when expressed as a decimal. Multiplying this by 100 gives us the percentage of 67%.
11.

After attending a retirement party for the Behavioral Sciences Department Chairperson, many of the faculty developed gastroenteritis. All attendees were interviewed by the local public health nurse who had completed a Principles of Epidemiology selfstudy course. The table shows the results of the interviews. Calculate the appropriate measure of association for each of the homemade food items shown in the table above. For which food is the measure of association the largest?
Correct Answer
D. Ice Cream
Explanation
The measure of association for each food item is calculated based on the number of people who ate the food and developed gastroenteritis. The largest measure of association indicates the highest association between consuming the food item and developing gastroenteritis. Therefore, the explanation for the correct answer, which is Ice Cream, is that it had the highest number of people who ate it and developed gastroenteritis compared to the other food items.
12.
A comparison of clinically diagnosed versus autopsyconfirmed gastric and peptc ulcers was performed on 100,000 consecutive diseased patients in several large hospitals as shown in the following table.
From these data, the sensitivity of clinical diagnosis was:
Correct Answer
D. 1,500/4,000
Explanation
The sensitivity of clinical diagnosis refers to the proportion of true positive cases that are correctly identified as positive by the clinical diagnosis. In this case, the numerator represents the number of clinically diagnosed gastric and peptic ulcers that were confirmed by autopsy (1,500), and the denominator represents the total number of autopsyconfirmed cases (4,000). Therefore, the correct answer is 1,500/4,000.
13.
A laboratory test has been developed to assess the risk of prostate cancer among men. Studies with human subjects involving repeated measures indicate that the test yields the same results for every individual again and again, However, other studies indicate that there is a very low correlation between this new test for prostate cancer and already existing tests with proven track records. The areas of relative strength and relative weakness of this new test respectively are:
Correct Answer
C. Reliability and validity
Explanation
The given question is asking about the areas of relative strength and relative weakness of the new test for prostate cancer. The information provided states that the test yields the same results for every individual repeatedly, indicating its reliability. However, there is a low correlation between this new test and existing tests with proven track records, suggesting a weakness in terms of validity. Therefore, the correct answer is reliability and validity.