# USMLE Step 1 Biostatistics Questions – Free Practice Qbank

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## Free USMLE Step 1 Biostatistics and Epidemiology Questions

Specificity for breast examination is traditionally rather high among community practitioners. If a team of new researchers set forth a goal to increase specificity in detection of breast cancer from the previously reported national average of 74%, based on the following results, has the team achieved their goal?

Breast Cancer Screening Results:

 Patients with breast cancer Patients without breast cancer Test is Positive (+) 21 5 Test is Negative (-) 7 23
1. No, the research team’s results lead to nearly the same specificity as the previous national average
2. Yes, the team has achieved an increase in specificity of approximately 8 %
3. Yes, the team has achieved an increase in specificity of over 15%
4. Cannot be determined, as the prevalence of breast cancer is not listed
5. Cannot be determined, since we do not know the numbers affiliated with the first trial
A 50-year-old male presents to the office for a routine health check-up. Managing his weight has been his focus at this time to improve his overall health. The doctor discusses his weight loss goals and overall health benefits from weight loss including better blood pressure management and decreased insulin resistance. The national average weight for males aged 50-59 years old is 90 kg (200 lb) with a standard deviation of 27 kg (60 lb). What would be the most likely expected value if his weight was 2 standard deviations above the mean?
1. 36 kg (80 lb)
2. 63 kg (140 lb)
3. 145 kg (320 lb)
4. 118 kg (260 lb)
5. 172 kg (380 lb)

A 19-year-old woman diagnosed with metastatic Ewing sarcoma. She has undergone multiple treatments without improvement. She decides to stop treatment and pursue only palliative care. She is of sound mind and has weighed the benefits and risks of this decisions. The patient’s mother objects and insist that treatments be continued. What should be done?

1. Continue treatments until the patient has a psychiatric evaluation
2. Follow the wishes of the patient’s mother as she has decision making power for the patient
3. Halt treatments and begin palliative care
4. Try to seek additional experimental treatments that are promising
5. Continue treatment because otherwise the patient will die

A research team is working on a new assay meant to increase the sensitivity of testing in cervical cancer. Current sensitivity is listed at 77%. If this research team’s latest work culminates in the following results (listed in table), has the sensitivity improved; and if so, then by what percentage?

Research Team’s Latest Results:

 Patients with cervical cancer Patients without cervical cancer Test is Positive (+) 47 4 Test is Negative (-) 9 44
1. No, the research team has not seen any improvement in sensitivity from the newest results
2. Yes, the research team has seen an improvement of more than 10% sensitivity, according to the new results listed
3. Yes, the research team has seen an improvement in sensitivity of almost 7%, according to new results listed
4. No, the research team has seen a decrease in sensitivity according to the newest listed results
5. Yes, the research team has seen an improvement of less than 2% sensitivity according to new results; this improvement is negligible and should be improved upon for significant contribution to the field

A 17-year-old boy presents to the office complaining of burning with urination and a purulent urethral discharge. The patient states that he has had unprotected sex with one partner who informed him recently that they had gonorrhea. The patient wanted to get treated right away but was afraid to because he does not want his parents to know he is sexually active. What is the most appropriate next step?

1. Inform the patient their parents must consent to his treatment
2. Inform the patient that you won’t tell his parents but that he cannot receive medical care without their consent
3. Treat the patient confidentiality
4. Treat the patient but inform his parents of the care he received
5. Contact child protective services
A 32-year-old man is being treated by a female psychiatrist for chronic depression. Recently, he has been scheduling more visits that are out of routine. He does not report any symptoms or problems with SSRI medications during these visits. Upon further questioning, he confesses that he is attracted to her and says “You are the only one on Earth who understands me.” He expresses desire to date her. What is the most appropriate next step in management?
1. Re-evaluate patient for borderline personality disorder
2. Ask closed-ended questions and use a chaperone for future visits
3. Switch him to another provider to avoid further communication
4. Increase dosage of SSRI
5. Date him, but inform the medical ethics committee board

A 43-year-old male presents to the office for hypertension follow-up. He was recently diagnosed and has been managing with diet modification and moderate intensity exercise. Today he brings a list of his recent at home morning blood pressure readings. Readings for his systolic blood pressure over the last 5 days are:

• Day 1: 130 mm Hg
• Day 2: 132 mm Hg
• Day 3: 128 mm Hg
• Day 4: 132 mm Hg
• Day 5: 128 mm Hg

What is the most likely standard deviation for these systolic blood pressure readings?

1. 1 mm Hg
2. 1.5 mm Hg
3. 4 mm Hg
4. 2 mm Hg
5. 2.5 mm Hg
Biomedical and behavioral research studies are the cornerstone to modern, allopathic medicine. The treatments and management protocols we use everyday are dependent on the empirical evidence from research trials. What is the purpose of third party committees like the Institutional Review Board (IRB) regarding research studies?
1. Resolve refusal of treatment disputes between patient’s family and provider
2. Publish peer-reviewed research papers on current medical advances
3. Assess the thoroughness of informed consent given to patient
4. Hold educational activities and seminars on various health issues for the general public

In order to study the association between coffee drinking and subsequent development of lung cancer, the researchers decided to carry out a multicentric case-control study with a large number of participants—800 of them with the diagnosis of lung cancer, and 800 of them as age-adjusted controls. According to the results delineated in Table 1, 80% of those with lung cancer were regular coffee-drinkers, which resulted in an odds ratio of 23. This brought researchers to conclusion that the regular consumption of coffee is strongly linked to lung cancer development; however, which systematic error they did not take into account?

Table 1. Contingency table of coffee drinking in relation to the presence of lung cancer

 Lung cancer present Lung cancer absent Coffee drinking 640 120 No coffee drinking 160 680

1. Observer bias
2. Selection bias
3. Confounding bias
4. Attrition bias
5. Information bias
In a community of 5000, 40 people from 40 different households develop an infection with a new strain of influenza virus having an incubation period of 7 days. The total number of people in these households are 150. Ten days later, 90 new cases of the same disease are reported from these households. 25 more cases are reported from these households after a month. The total number of cases reported after a month from this community is 1024. What is the secondary attack rate for this infection?
1. (115/150) x 100
2. (115/1024) x 100
3. (90/110) x 100
4. (90/150) x 100
5. (90/5000) x 100

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