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Question 1
Incorrect
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You performed pelvic ultrasound of Mrs Aciman as she had pelvic bloating and intermittent pain. The ultrasound shows a complex ovarian cyst and the radiologist who reported the results has advised urgent consultation with a gynaecologist. Upon breaking the news to Mrs Aciman you learn that she recently had a blood test done that was normal. You explain it to her that the test performed (Ca-125) is not always perfect and is only able to detect 80% of the cancer cases while the remaining 20% go undetected.
Which statistical term appropriately explains the 80% in this example.Your Answer: Specificity
Correct Answer: Sensitivity
Explanation:Tests are used to confirm the presence of a particular disease. However the results can be misleading at times since most of the tests have some limitations associated with them.
Sensitivity is the correct term that refers to the probability of a positive test. The others are explained below:False Positive rates refer to the proportion of the patients who don’t have the condition being detected as positive.
False Negative rates refer to the proportion of the patients who have the condition being detected as negative (like the 20% of the patients that went undetected by the Ca-125 test).
Specificity describes the ability of a test to detect and pick up people without the disease. Absolute risk ratio compares the rate of two separate outcomes.
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This question is part of the following fields:
- Statistical Methods
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Question 2
Correct
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A study was concerned with finding out the normal reference range of IgE levels in adults was conducted. Presuming that the curve follows a normal distribution, what is the percentage of individuals having IgE levels greater than 2 standard deviations from mean?
Your Answer: 2.30%
Explanation:Since the data is normally distributed, 95.4% of the values lie with in 2 standard deviations from mean. The rest of the 4.6% are distributed symmetrically outside of that range which means 2.3% of the values lie above 2 standard deviations of the mean.
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This question is part of the following fields:
- Statistical Methods
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Question 3
Incorrect
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In a study lasting over a period of two years, in which the mean age of 800 patients was 82 years, the efficacy of hip protectors in reducing femoral neck fractures was discussed.
Both experimental and control group had 400 members. Instances of fractures reported over the two year time duration were 10 for the control group (that were prescribed hip protector) and 20 for the control group.
What is the value of Absolute Risk Reduction?Your Answer: 2
Correct Answer: 0.025
Explanation:ARR= (Risk factor associated with the new drug group) — (Risk factor associated with the currently available drug)
So,
ARR= (10/400)-(20/400)
ARR= 0.025-0.05
ARR= 0.025 (Numerical Value)
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This question is part of the following fields:
- Statistical Methods
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Question 4
Incorrect
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A graph is created to show the exponential relationship between bacterial growth (y-axis) and time (x-axis).
Which of the following statements is most true about this kind of exponential relationship?Your Answer: As x increases the increase in y is proportional to y
Correct Answer: y = ex
Explanation:The relationship between bacterial growth and time is a tear-away exponential. The mathematical relationship between y and x in this case is:
y = ex
Where: the power is x, and the base is e.
Euler’s number (e) is a mathematical constant that is the base for all logarithms occurring naturally. Its value is 2.718.
The statement X increasing with an increase in Y is proportional to Y refers to the change in y in terms of x when considering any exponential relationship.
This is not a build-up exponential, and that is mathematically stated as y = 1-e-kt.
The negative x axis being a horizontal asymptote and the y intercept being 0, 1 are examples of tearaway exponentials , but do not describe an exponential process.
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This question is part of the following fields:
- Statistical Methods
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Question 5
Incorrect
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In reference to confounding variables, which among the given is not true?
Your Answer: Age and sex are common confounders
Correct Answer: In the analytic stage of a study confounding can be controlled for by randomisation
Explanation:Randomisation can be used to provide control over the confounding variables during the design stage of a study however during analytical stage a technique called stratification is used for controlling confounding variables. Since the question asks for the information that is factually incorrect.
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This question is part of the following fields:
- Statistical Methods
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Question 6
Correct
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Drug X, a new intravenous induction drug, is being administered as a bolus at regular time intervals, and the following data were observed:
Time following injection (hours) vs Plasma concentration of drug X (mcg/mL)
2 / 400
6 / 100
10 / 25
14 / 6.25
Which of the following values estimate the plasma half-life (T½) of drug X?
Your Answer: 2 hours
Explanation:Half life (T½) is the time required to change the amount of drug in the body by one-half (or 50%) during elimination. The time course of a drug in the body will depend on both the volume of distribution and the clearance.
Extrapolating the values from the plasma concentration vs time:
Plasma concentration at 0 hours = 800 mcg/mL
Plasma concentration at 2 hours = 400 mcg/mL
Plasma concentration at 4 hours = 200 mcg/mL
Plasma concentration at 6 hours = 100 mcg/mL
Plasma concentration at 8 hours = 50 mcg/mL
Plasma concentration at 10 hours = 25 mcg/mL
Plasma concentration at 12 hours = 12.5 mcg/mL
Plasma concentration at 14 hours = 6.25 mcg/mL -
This question is part of the following fields:
- Statistical Methods
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Question 7
Incorrect
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Among the following options which one compares variance within the group and variance between groups?
Your Answer: Mann Whitney U
Correct Answer: ANOVA
Explanation:ANOVA is based upon within group variance (i.e. the variance of the mean of a sample) and between group variance (i.e. the variance between means of different samples). The test works by finding out the ratio of the two variances mentioned above. (Commonly known as F statistic).
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This question is part of the following fields:
- Statistical Methods
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Question 8
Correct
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A randomized controlled trail has been conducted to compare two drugs used for the early management of acute severe asthma in the emergency department. After being allocated to the randomized groups, many patients have been excluded due to deleterious effect to the drugs.
How the data would be analysed?Your Answer: Include the patients who drop out in the final data set
Explanation:Randomized controlled trails will be analysed by the intention-to-treat (ITT) approach. It provides unbiased comparisons among the treatment groups. ITT analyses are done to avoid the effects of dropout, which may break the random assignment to the treatment groups in a study.
ITT analysis is a comparison of the treatment groups that includes all patients as originally allocated after randomization.
In order to include such participants in an analysis, outcome data could be imputed which involves making assumptions about the outcomes in the lost participants.
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This question is part of the following fields:
- Statistical Methods
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Question 9
Correct
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A 26-year-old doctor has recently been diagnosed with lung cancer. He would like to find out his survival time for the condition.
Which statistical method is used to predict survival rate?Your Answer: Kaplan-Meier estimator
Explanation:The Weibull distribution are used to describe various types of observed failures of the components. it is used in reliability and survival analysis.
Regression Analysis is used to measure the relationship between among two or more variable. It determines the effect of independent variables on the dependent variables.
Student t-test is one of the most commonly used method to test the hypothesis. It determines the significant difference between the means of two different groups.
A time series is a collection of observations of well-defined data obtained at regular interval of time.
Kaplan-Meier estimator is used to estimate the survival function from lifetime data. It can be derived from maximum likelihood estimation of hazard function. It is most likely used to measure the fraction of patient’s life for a certain amount of time after treatment.
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This question is part of the following fields:
- Statistical Methods
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Question 10
Correct
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A study involving 64 patients of diabetes mellitus type 2 was performed. Weight of each patient was recorded and the mean weight of the patients was found to be 81 kg. The data set had a standard deviation of 12 kg.
The value of standard error associated with the mean is:Your Answer: 1.5
Explanation:Standard error can be calculated by the following formula:
Standard Error= (Standard Deviation)/√(Sample Size)
= (12) / √(64)
= 12 / 8
= 1.5 -
This question is part of the following fields:
- Statistical Methods
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SESSION STATS - PERFORMANCE PER SPECIALTY
