Biostatistics Practice Questions

Q: What is the probability of selecting a patient who requires surgery from a total of 50 admissions, where 10 girls and 20 boys needed surgery?

3/5. ***3/5*** - The total number of patients requiring surgery is the sum of girls and boys who needed surgery: **10 (girls) + 20 (boys) = 30 patients**. - The probability is calculated by dividing the number of favorable outcomes (patients needing surgery) by the total number of possible outcomes (total admissions): **30 / 50 = 3/5**. *3/10* - This option would be correct if only 15 patients (e.g., 5 girls and 10 boys) needed surgery out of 50 admissions. - It incorrectly calculates the proportion of patients requiring surgery relative to the total admissions. *1/2* - This option would imply that **25 out of 50** patients required surgery, which contradicts the given numbers. - It represents a **50% probability**, which is not supported by the calculation of 30 patients out of 50. *1/3* - This option would be correct if approximately **17 out of 50** patients needed surgery (16.67 rounded), which is not the case here. - It misrepresents the ratio of patients needing surgery to the total admissions, as **30/50 simplifies to 3/5, not 1/3**.

Q: What is the shape of a normal distribution curve?

Bell-shaped. ***Bell-shaped*** - A **normal distribution** is a **symmetric probability distribution** centered around its mean, with tails that taper off indefinitely. - The distinctive shape resembles a **bell**, with the highest point at the mean and gradually decreasing frequencies as values move away from the mean. *J-shaped* - A **J-shaped curve** typically describes a distribution where the frequency is highest at one end and then continuously decreases or increases to the other end. - This shape is not characteristic of the **symmetry** and **central tendency** observed in a normal distribution. *U-shaped* - A **U-shaped curve** indicates that frequencies are highest at both ends of the distribution and lowest in the middle. - This is the opposite of a **normal distribution**, where the highest frequency is at the center (mean). *None of the options* - The term **bell-shaped** accurately describes a normal distribution curve, making this option incorrect.

Q: What is the probability that a value chosen from a community will be above the median?

0.5. ***0.5*** - The **median** is defined as the value that divides a dataset into two equal halves. - This means that **50% of the values** in the dataset are below the median, and **50% are above** the median. *0.25* - This would imply that only 25% of the data lies above the median, which contradicts its definition as the midpoint. - The value 0.25 is typically associated with **quartiles**, not the median. *0.6* - This indicates that 60% of the values are above the median, which is inconsistent with the median's role in splitting data evenly. - Such a probability would suggest that the chosen value falls into the **upper 60% segment**, not simply above the median. *1* - A probability of 1 means that it is **certain** for a value to be above the median, which is incorrect. - This would only be true if all observed values were greater than the median, which is not possible as the median itself is a data point or derived from data points.

Q: In a clinical study evaluating a new diagnostic test for a disease, the test was found to have 60 true positives out of 100 positive results. What is the positive predictive value of the test?

60/100. ***60/100*** - The **positive predictive value (PPV)** is the proportion of **true positives** among all positive test results. - Given 60 true positives out of 100 positive results, the calculation is 60 divided by 100. *40/100* - This value would represent the number of **false positives** (positive test results that are actually negative) out of all positive test results, which is not the positive predictive value. - The PPV is specifically concerned with the reliability of a positive result indicating the presence of the disease. *40/300* - This fraction does not correspond to a standard measure of diagnostic test validity given the provided information regarding true positives and total positive results. - It might incorrectly combine disparate data points or represent a miscalculation based on other variables not supplied. *240/300* - This value is not derived from the provided numbers for true positives and total positive results in the context of positive predictive value. - It could potentially represent sensitivity or specificity calculations, but it is not the **positive predictive value**.

Q: Which of the following is not a characteristic of a systematic review?

Meta analysis is always performed. ***Meta-analysis is always performed*** - While **meta-analysis** is frequently a component of a systematic review, it is not always performed; it is only feasible when the included studies are sufficiently homogeneous and quantitative synthesis is appropriate. - A systematic review can identify, appraise, and synthesize evidence without statistically combining results, especially when studies are too **heterogeneous**. *Search for literature is compulsory using explicit search strategy* - A **comprehensive and explicit search strategy** is a defining characteristic of a systematic review, ensuring all relevant literature is included and bias is minimized. - This systematic approach helps to identify all studies on a given topic, regardless of their outcome. *Research questions always focused* - Systematic reviews are driven by **clearly defined and focused research questions** (often in PICO format: Population, Intervention, Comparison, Outcome) to guide the search, selection, and analysis processes. - A focused question ensures the review has a narrow scope, allowing for a thorough and relevant synthesis of the evidence. *Critical appraisal is always criteria-based* - **Critical appraisal** using predefined criteria (e.g., risk of bias tools) is a mandatory step in a systematic review to evaluate the methodological quality and validity of the included studies. - This systematic assessment helps to determine the strength of the evidence and its applicability.

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

What is the probability of selecting a patient who requires surgery from a total of 50 admissions, where 10 girls and 20 boys needed surgery?

Accepted Answer

3/5

Answer

3/10

Answer

1/2

Answer

1/3

Question 2

In the context of medical screening, how does a series testing approach affect the net sensitivity and net specificity of the screening methods?

Accepted Answer

Net sensitivity is decreased and net specificity is increased

Answer

Net sensitivity and net specificity are both increased

Answer

Net sensitivity is increased and net specificity is decreased

Answer

Net sensitivity remains the same and net specificity is increased

Question 3

What does the term 'validity' mean in the context of indicators?

Accepted Answer

It accurately measures the concept it is intended to assess.

Answer

Indicators should reflect changes in the situation being evaluated.

Answer

Indicators must be capable of collecting relevant data.

Answer

The measurement should yield consistent results across different evaluators under similar conditions.

Question 4

What is the shape of a normal distribution curve?

Accepted Answer

Bell-shaped

Answer

J-shaped

Answer

U-shaped

Answer

None of the options

Question 5

What is the probability that a value chosen from a community will be above the median?

Accepted Answer

0.5

Answer

1

Answer

0.25

Answer

0.6

Question 6

In a clinical study evaluating a new diagnostic test for a disease, the test was found to have 60 true positives out of 100 positive results. What is the positive predictive value of the test?

Accepted Answer

60/100

Answer

40/100

Answer

40/300

Answer

240/300

Question 7

Which of the following is not a characteristic of a systematic review?

Accepted Answer

Meta analysis is always performed

Answer

Search for literature is compulsory using explicit search strategy

Answer

Critical appraisal is always criteria based

Answer

Research questions always focused

Question 8

Which of the following statements accurately describes a characteristic of a random sample?

Accepted Answer

Any member of a group to be studied has an equal chance of being included in the study.

Answer

Every nth name on a list is selected in a systematic manner.

Answer

Subjects in the study are volunteers who choose to participate.

Answer

A person in a control group cannot be a member of the experimental group.

Question 9

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 10

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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