Biostatistics Practice Questions

Q: Which of the following is a disadvantage of non-randomized trials?

Degree of comparability is low. ***Degree of comparability is low*** - Non-randomized trials have a **lower degree of comparability** between intervention and control groups because subjects are not randomly assigned, making it more difficult to attribute observed differences solely to the intervention. - This lack of comparability increases the risk of **confounding variables** influencing the results, as baseline characteristics of the groups may differ significantly. *Random assignment of subjects* - This is a *feature of randomized controlled trials (RCTs)*, not a disadvantage of non-randomized trials. RCTs use random assignment to create comparable groups. - In non-randomized trials, **random assignment is absent**, which is precisely why comparability can be low. *The experiment can serve as its own control or can utilize a natural control* - This describes a potential **advantage or characteristic of certain non-randomized designs**, like before-and-after studies or natural experiments. - While it can be useful in some contexts, it does not mitigate the fundamental issue of **low comparability** in non-randomized designs when comparing different groups. *Several trials may be needed before evaluation is considered conclusive.* - This statement applies broadly to many types of research, including some randomized trials, and indicates the need for **replication and robust evidence**. - While non-randomized trials might indeed require more supportive evidence due to their inherent limitations, this is a general research principle and not a unique disadvantage stemming from non-randomization itself, compared to the direct impact on comparability.

Q: What is the neonatal mortality rate in a population where there were 4050 total births, 50 stillbirths, and 150 total neonatal deaths within the first 28 days of life (which includes 50 deaths within the first 7 days)?

37.5. ***37.5*** - **Neonatal mortality rate (NMR)** is calculated as deaths occurring within the first **28 completed days of life** per 1000 live births. - **Calculation**: Live births = 4050 total births - 50 stillbirths = 4000; NMR = (150 total neonatal deaths / 4000 live births) × 1000 = **37.5 per 1000 live births**. *30.0* - This incorrect value represents a **miscalculation** that doesn't correspond to any logical subset of the given data in the question. - **Error**: Even using only early neonatal deaths (50 deaths in first 7 days) would yield (50/4000) × 1000 = **12.5**, not 30.0, indicating a fundamental computational error. *45.0* - This value incorrectly includes **stillbirths** in the numerator or uses wrong denominators in the calculation. - **Error**: Stillbirths are **not counted** in neonatal mortality; only deaths after live birth are included in NMR calculations. *25.0* - This represents a significant **undercounting** of neonatal deaths, possibly using only partial death data. - **Error**: Fails to account for the complete **150 neonatal deaths** within 28 days, leading to substantial underestimation.

Q: In a cohort study conducted with 100 individuals in each group (exposed and non-exposed), out of those exposed to the risk factor, 10 are diseased, and out of those not exposed to the risk factor, only 5 are diseased. What is the relative risk?

2. ***Correct Option: 2*** - The **incidence in the exposed group** is 10/100 = 0.1. - The **incidence in the non-exposed group** is 5/100 = 0.05. - **Relative risk (RR)** is calculated as the ratio of the incidence in the exposed group to the incidence in the non-exposed group: 0.1 / 0.05 = 2. - This indicates that the **exposed group has twice the risk** of developing the disease compared to the non-exposed group. *Incorrect Option: 1.5* - This value would be obtained if the ratio of incidences was 0.075 / 0.05 or 0.1/0.066, which is not consistent with the given data. - An RR of 1.5 indicates a **lesser strength of association** than what is observed in this study. *Incorrect Option: 0.75* - This value would result if the incidence in the exposed group was *lower* than in the non-exposed group (e.g., 0.05 / 0.066), suggesting a **protective effect**. - An RR < 1 implies that exposure is protective rather than a risk factor, which contradicts the given data. *Incorrect Option: 1* - A **relative risk of 1** indicates there is no difference in the risk of disease between the exposed and non-exposed groups. - This would mean the incidence rate in both groups is identical (e.g., 0.1 / 0.1 = 1), which contradicts the provided data where exposed group has higher incidence.

Q: Which of the following is a non-probability sampling method?

Quota sampling. ***Quota sampling*** - In **quota sampling**, researchers select participants based on specific characteristics (e.g., age, gender, ethnicity) to ensure the sample reflects the population proportions of these characteristics. - This method is **non-probability** because the selection of individuals within each quota is not random, and not every member of the population has an equal chance of being selected. *Simple random sampling* - **Simple random sampling** is a **probability sampling method** where every member of the population has an equal and independent chance of being selected. - This is typically achieved through random number generators or drawing names from a hat. *Systematic random sampling* - **Systematic random sampling** is a **probability sampling method** where sample members are selected at regular intervals from a list of the population. - The starting point is chosen randomly, but subsequent selections follow a predetermined pattern, ensuring a systematic, yet random, selection. *Cluster sampling* - **Cluster sampling** is a **probability sampling method** where the population is divided into naturally occurring groups (clusters), and then a random sample of these clusters is chosen. - Once clusters are selected, all individuals within the chosen clusters, or a random sample of individuals from them, are included in the study.

Q: APGAR scores of 30 children are recorded in a hospital, and most of the readings are found to be 7 or above. What can be inferred about this data distribution?

Negatively skewed data. ***Negatively skewed data*** - A distribution is **negatively skewed** when the bulk of the data is concentrated at the **higher end** of the scale - In this case, most **APGAR scores are 7 or above** (out of maximum 10), indicating a **left-skewed or negatively skewed distribution** - The tail of the distribution extends toward the **lower values**, while the peak is at the **higher end** - In negatively skewed data: **Mean < Median < Mode** *Positively skewed data* - **Positively skewed data** would imply that most APGAR scores were at the **lower end** of the scale, with a tail extending toward higher values - This is contrary to the observation that most scores are 7 or above - In positively skewed data: **Mode < Median < Mean** *Normal distribution* - A **normal distribution** implies a **symmetrical bell-shaped curve** where data is evenly distributed around the mean - The description "most readings are 7 or above" clearly indicates an **asymmetrical distribution**, not a normal one - In normal distribution: **Mean = Median = Mode** *Symmetrical data* - **Symmetrical data** means the distribution is balanced, with equal spread on both sides of the center - The given condition that most readings are at the **higher end (7 or above)** signifies an **imbalance**, ruling out symmetry

Question 1

Which of the following is a disadvantage of non-randomized trials?

Accepted Answer

Degree of comparability is low

Answer

Random assignment of subjects

Answer

The experiment can serve as its own control or can utilize a natural control

Answer

Several trials may be needed before evaluation is considered conclusive.

Question 2

What is the neonatal mortality rate in a population where there were 4050 total births, 50 stillbirths, and 150 total neonatal deaths within the first 28 days of life (which includes 50 deaths within the first 7 days)?

Accepted Answer

37.5

Answer

30.0

Answer

45.0

Answer

25.0

Question 3

In a cohort study conducted with 100 individuals in each group (exposed and non-exposed), out of those exposed to the risk factor, 10 are diseased, and out of those not exposed to the risk factor, only 5 are diseased. What is the relative risk?

Accepted Answer

2

Answer

1.5

Answer

0.75

Answer

1

Question 4

Which of the following is a non-probability sampling method?

Accepted Answer

Quota sampling

Answer

Simple random sampling

Answer

Systematic random sampling

Answer

Cluster sampling

Question 5

APGAR scores of 30 children are recorded in a hospital, and most of the readings are found to be 7 or above. What can be inferred about this data distribution?

Accepted Answer

Negatively skewed data

Answer

Positively skewed data

Answer

Normal distribution

Answer

Symmetrical data

Biostatistics — MCQs

Biostatistics — MCQs

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