Biostatistics Practice Questions

Q: Which study design is most effective for investigating rare adverse effects of a drug?

Case-control study. ***Case-control study*** - This design starts by identifying individuals with the **rare adverse effect (cases)** and a control group without the effect to look back for exposure to the drug. - It is efficient for studying rare outcomes because it doesn't require following a large population for a long time to observe few events. *Cohort study* - A **cohort study** follows a group of individuals exposed and unexposed to a drug forward in time to observe outcomes. - While good for common outcomes, it would require an **extremely large sample size** and a long follow-up period to observe rare adverse drug effects. *Cross-sectional study* - A **cross-sectional study** assesses exposure and outcome simultaneously at a single point in time. - This design is suitable for determining **prevalence** but cannot establish temporal relationships between drug exposure and rare adverse effects, nor is it efficient for rare outcomes. *Clinical trial/experimental study* - **Clinical trials** are primarily designed to test the efficacy and safety of new interventions, usually focusing on common adverse effects. - They are generally **not powered** or long enough to detect rare adverse events, as such events would occur in very few participants, if any.

Q: In a community of 1,000,000 population, 105 children were born in a year, out of which 5 were stillbirths and 4 died within the first year of life. What is the Infant Mortality Rate (IMR)?

40. ***40*** - **Infant Mortality Rate (IMR)** = (Deaths in first year of life / Live births) × 1,000 - Live births = Total births - Stillbirths = 105 - 5 = **100** - IMR = (4 / 100) × 1,000 = **40 per 1,000 live births** - Stillbirths are excluded from both numerator and denominator as IMR only counts deaths after live birth *90* - This would result from incorrectly using total births (105) instead of live births (100) in the denominator - Wrong calculation: (4 / 105) × 1,000 ≈ 38, not 90 - This option represents a common error but with incorrect arithmetic *120* - This could result from including stillbirths in the numerator: (5+4) / 100 × 1,000 = 90, not 120 - Or from other miscalculations mixing up the numerator and denominator - Does not follow the standard IMR formula *150* - This represents a significant calculation error - May result from using wrong base (per 100 instead of per 1,000) or including stillbirths incorrectly - Such high IMR does not match the given data of 4 infant deaths per 100 live births

Q: Bladder cancer can occur in those who are working in dye industry for 25 years. Which study design is most appropriate for establishing a causal relationship between dye industry work and bladder cancer?

Cohort study. ***Cohort study*** - A **cohort study** tracks a group of individuals exposed to a risk factor (dye industry work) and a group not exposed over time to see who develops the outcome (bladder cancer). - This design allows for the calculation of **incidence rates** and relative risk, which are crucial for establishing a causal link, especially when the exposure is rare or specific. - Cohort studies establish **temporal relationship** (exposure precedes disease) and can demonstrate a **dose-response relationship**, both essential for proving causality. *Cross-sectional study* - A **cross-sectional study** assesses exposure and outcome simultaneously at a single point in time, making it difficult to determine the temporal sequence of events. - While it can identify associations, it cannot definitively establish a **cause-and-effect relationship** because it doesn't observe outcomes developing over time. *Case-control study* - A **case-control study** compares individuals with the outcome (cases) to individuals without the outcome (controls) and retrospectively looks for differences in past exposures. - While useful for studying **rare diseases** and can suggest associations, it is prone to **recall bias** regarding exposure history and cannot establish causality as definitively as cohort studies. *Randomized control trial* - A **randomized controlled trial (RCT)** involves randomly assigning participants to an intervention group or a control group and following them prospectively. - While RCTs provide the strongest evidence for causality, it would be **unethical** to intentionally expose people to a known carcinogen like dye industry chemicals for research purposes.

Q: What is a key benefit of Randomized Controlled Trials (RCTs) in clinical research?

They minimize selection bias.. ***They minimize selection bias.*** - **Randomization** in RCTs ensures that participants have an equal chance of being assigned to any of the treatment groups, thereby balancing potential **confounding factors** across groups. - This balance helps to ensure that any observed differences in outcomes between groups are more likely due to the intervention being studied rather than pre-existing differences among participants, thus minimizing **selection bias**. *They can be conducted more quickly than other study types.* - RCTs often require **extensive planning**, recruitment, and follow-up periods, making them one of the **most time-consuming** study designs. - The need for sufficient **power** to detect meaningful differences often translates into longer study durations. *They are ideal for studying rare diseases.* - Due to the requirement for **large sample sizes** to demonstrate statistical significance, RCTs are **not practical** for diseases with low prevalence. - Recruiting enough participants with a rare disease for an RCT can be extremely challenging and often **unfeasible**. *They are generally less expensive than other study types.* - RCTs are typically among the **most expensive** study designs because they involve extensive participant recruitment, intervention administration, data collection, and long-term follow-up. - The costs associated with staff, resources, and monitoring for ethical compliance contribute to their **high financial burden**.

Q: Which of the following is an example of a case-control study?

PVC exposure and angiosarcoma of the liver. ***PVC exposure and angiosarcoma of the liver*** - This is a classic example of a **case-control study** where individuals with a rare disease (angiosarcoma of the liver) are identified (cases) and compared to a control group without the disease to determine past exposures (PVC). - The study looked back in time to identify differences in exposure between cases and controls. *Framingham heart study (cohort study)* - The Framingham Heart Study is a well-known **prospective cohort study** that has followed participants over time to observe the development of cardiovascular disease. - In a cohort study, researchers identify a group of individuals and follow them forward in time to see who develops the outcome of interest, making it different from a case-control design. *Doll & Hill Study (cohort study)* - The Doll & Hill study is a landmark **cohort study** that investigated the association between smoking and lung cancer by following a group of British doctors over several years. - This study started with healthy individuals and observed them over time to see who developed lung cancer, which is characteristic of a cohort design. *Thalidomide exposure and its association with teratogenicity* - While the thalidomide tragedy led to crucial epidemiological investigations, the initial identification of the association was often through **case series** or **descriptive epidemiology**, noting an unusual clustering of rare birth defects among infants whose mothers took thalidomide. - Subsequent studies might have incorporated case-control elements, but the prompt asks for an example of a case-control study, and this event itself is generally cited for its role in pharmacovigilance and observational studies rather than a single, classic case-control study example in the way "PVC and angiosarcoma" is.

Q: Which of the following is the MOST important vital statistic in a population?

Mortality rate. ***Mortality rate*** - The **mortality rate** directly reflects the health status and overall well-being of a population by indicating the number of deaths per unit population. - A high mortality rate signals underlying public health issues, inadequate healthcare, or poor living conditions, making it the **most critical vital statistic** for assessing population health and guiding interventions. - It serves as a **key indicator** for comparing health status across populations and time periods. *Fertility rate* - The **fertility rate** measures the average number of children born to women of reproductive age, influencing future population size and age structure. - While important for demographic planning and population projections, it doesn't directly provide insights into the immediate health challenges or mortality burden of a population. *Morbidity rate* - The **morbidity rate** quantifies the incidence or prevalence of disease in a population, reflecting the disease burden. - Although crucial for understanding health problems and planning healthcare services, it is considered secondary to mortality as a vital statistic since mortality represents the ultimate health outcome. *Birth rate* - The **birth rate** quantifies the number of live births per 1,000 people in a year, contributing to population growth and demographic trends. - Like the fertility rate, it is essential for understanding natality patterns but offers less insight into the overall health status and survival of a population compared to the mortality rate.

Q: In a clinical study examining the relationship between weight and height in pediatric patients, what is the maximum possible value of the correlation coefficient if the correlation is very strong?

+1. ***+1 (perfect positive correlation)*** - A correlation coefficient of **+1** indicates a perfect positive linear relationship between two variables, meaning as one variable increases, the other increases proportionally. - This value represents the **maximum possible strength** for a positive correlation. *0* - A correlation coefficient of **0** indicates no linear relationship between two variables. - This would contradict the premise that the correlation is "very strong". *+2 (invalid value for correlation coefficient)* - The correlation coefficient, also known as Pearson's r, can only range from **-1 to +1**. - A value of +2 is outside this possible range and is therefore an **invalid value**. *No correlation (not possible for strong correlation)* - **No correlation** implies a correlation coefficient of 0 or close to 0. - This directly contradicts the statement that there is a **very strong correlation** between weight and height.

Q: The population is divided into homogeneous subgroups, and then individuals are randomly selected from each subgroup. What type of sampling is this?

Stratified random. ***Stratified random*** - In **stratified random sampling**, the population is first divided into homogeneous subgroups (strata), and then a simple random sample is drawn from each stratum. - This method ensures representation from all subgroups, which is implied by the description "separated into groups, from each group people are selected randomly." *Simple random* - **Simple random sampling** involves selecting individuals from an entire population purely by chance, where each individual has an equal probability of being chosen. - This method does not involve an initial division of the population into distinct groups before selection. *Systematic random* - **Systematic random sampling** involves selecting every nth individual from a list after a random starting point. - This method does not involve dividing the population into groups and then sampling from each group. *Cluster* - **Cluster sampling** involves dividing the population into clusters (usually naturally occurring groups), randomly selecting a few clusters, and then sampling *all* individuals within the selected clusters. - In cluster sampling, individuals are not randomly selected *from each* group; instead, entire groups are selected.

Q: What is the type of sampling used when a random sample is taken from distinct groups within a population, such as religious groups like Hindus, Muslims, and Christians?

Stratified random. ***Stratified random*** - This method involves dividing the population into **distinct, non-overlapping subgroups (strata)** based on a shared characteristic (e.g., religious groups). - A **random sample** is then drawn from each stratum, ensuring representation from all groups. *Simple random* - Involves selecting individuals entirely at **random** from the entire population, with each individual having an equal chance of being chosen. - It does not guarantee representation from specific subgroups within the population. *Systematic random* - This method selects individuals at **regular intervals** from a randomly ordered list of the population (e.g., every 10th person). - While it offers a degree of randomness, it does not specifically account for or ensure representation of distinct subgroups. *Cluster* - This method involves dividing the population into **clusters (natural groupings)**, usually geographically, and then randomly selecting entire clusters to sample. - Unlike stratified sampling, where individuals are selected from each stratum, cluster sampling involves sampling all individuals within chosen clusters.

Question 1

Which of the following statements is true regarding a combined prospective-retrospective study?

Accepted Answer

Retrospective identification of cohort followed by prospective follow-up

Answer

Only prospective follow-up from current time point

Answer

Cross-sectional assessment at a single time point

Answer

Only retrospective data collection from past records

Question 2

Which study design is most effective for investigating rare adverse effects of a drug?

Accepted Answer

Case-control study

Answer

Cohort study

Answer

Cross-sectional study

Answer

Clinical trial/experimental study

Question 3

In a community of 1,000,000 population, 105 children were born in a year, out of which 5 were stillbirths and 4 died within the first year of life. What is the Infant Mortality Rate (IMR)?

Accepted Answer

40

Answer

90

Answer

120

Answer

150

Question 4

Bladder cancer can occur in those who are working in dye industry for 25 years. Which study design is most appropriate for establishing a causal relationship between dye industry work and bladder cancer?

Accepted Answer

Cohort study

Answer

Cross-sectional study

Answer

Case-control study

Answer

Randomized control trial

Question 5

What is a key benefit of Randomized Controlled Trials (RCTs) in clinical research?

Accepted Answer

They minimize selection bias.

Answer

They can be conducted more quickly than other study types.

Answer

They are ideal for studying rare diseases.

Answer

They are generally less expensive than other study types.

Question 6

Which of the following is an example of a case-control study?

Accepted Answer

PVC exposure and angiosarcoma of the liver

Answer

Framingham heart study

Answer

Doll & Hill Study

Answer

Thalidomide exposure and its association with teratogenicity

Question 7

Which of the following is the MOST important vital statistic in a population?

Accepted Answer

Mortality rate

Answer

Fertility rate

Answer

Morbidity rate

Answer

Birth rate

Question 8

In a clinical study examining the relationship between weight and height in pediatric patients, what is the maximum possible value of the correlation coefficient if the correlation is very strong?

Accepted Answer

+1

Answer

0

Answer

+2

Answer

No correlation

Question 9

The population is divided into homogeneous subgroups, and then individuals are randomly selected from each subgroup. What type of sampling is this?

Accepted Answer

Stratified random

Answer

Simple random

Answer

Cluster

Answer

Systematic random

Question 10

What is the type of sampling used when a random sample is taken from distinct groups within a population, such as religious groups like Hindus, Muslims, and Christians?

Accepted Answer

Stratified random

Answer

Simple random

Answer

Cluster

Answer

Systematic random

Biostatistics — MCQs

Biostatistics — MCQs

On this page

Practice by Chapter

Want unlimited practice?