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Question 1
Incorrect
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Regarding relationships between two variables, what does a negative correlation coefficient indicate:
Your Answer: There is no correlation between the two variables
Correct Answer: The two variables are inversely related
Explanation:A negative correlation coefficient means that the two variables are inversely related e.g. socio-economic class and mortality.
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This question is part of the following fields:
- Evidence Based Medicine
- Statistics
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Question 2
Incorrect
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Which of the following is an example of discrete data:
Your Answer: Gender
Correct Answer: Number of children
Explanation:Discrete data is quantitative data that can only take whole numerical values e.g. number of children, number of days missed from work.
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This question is part of the following fields:
- Evidence Based Medicine
- Statistics
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Question 3
Correct
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Which of the following data types does a pain-scoring system represent?
Your Answer: Ordinal
Explanation:Pain scoring systems are processes for assessing pain and the severity of illnesses that have been scientifically designed and tested. An example of ordinal categorical data is a pain scoring system.
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This question is part of the following fields:
- Evidence Based Medicine
- Statistics
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Question 4
Correct
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A new test is being developed to diagnose chlamydia. 1000 people aged 15 – 35 years attending a GUM clinic undergo the new test and the current gold standard nucleic acid amplification test (NAAT) to confirm the diagnosis. Of the 1000 people, 250 are diagnosed with chlamydia. Of the patients diagnosed with chlamydia, 240 test positive with the new diagnostic test and of the patients not diagnosed with chlamydia, 150 test positive with the new diagnostic test. What is the positive predictive value of this test:Chlamydia YesChlamydia NoTotalPositive testa= 240b = 150390Negative testc = 10d = 600610Total2507501000
Your Answer: 0.62
Explanation:Positive predictive value (PPV) is the proportion of individuals with a positive test result who actually have the disease.Positive predictive value (PPV) = a/(a+b) = 240/390 = 0.62 = 62%This means there is a 62% chance, if the test is positive, that the patient actually has chlamydia.
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This question is part of the following fields:
- Evidence Based Medicine
- Statistics
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Question 5
Incorrect
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The results from the study investigating the accuracy of a new diagnostic test can be displayed in the following format. How is the positive predictive value calculated:Those with diseaseThose without diseaseTotalTest positiveaba+bTest negativecdc+dTotala+cb+dn=a+b+c+d
Your Answer:
Correct Answer: a/(a+b)
Explanation:Positive predictive value (PPV) is the proportion of individuals with a positive test result who actually have the disease.PPV = a/(a+b)
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This question is part of the following fields:
- Evidence Based Medicine
- Statistics
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Question 6
Incorrect
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The results from the study investigating the accuracy of a new diagnostic test can be displayed in the following format. How is the negative predictive value calculated:Those with diseaseThose without diseaseTotalTest positiveaba+bTest negativecdc+dTotala+cb+dn=a+b+c+d
Your Answer:
Correct Answer: d/(c+d)
Explanation:Negative predictive value (NPV) is the proportion of individuals with a negative test result who do not have the disease.NPV = d/(c+d)
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This question is part of the following fields:
- Evidence Based Medicine
- Statistics
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Question 7
Incorrect
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The interquartile range (IQ) is often displayed using which of the following:
Your Answer:
Correct Answer: Box and whisker plot
Explanation:A boxplot is a vertical or horizontal rectangle used to display the interquartile range, with the ends of the rectangle corresponding to the upper and lower quartiles of the data values. The box contains 50% of the data values. A line drawn through the rectangle corresponds to the median value. Whiskers, starting at the ends of the rectangle usually indicate the minimum and maximum values, therefore the entire box and whisker plot represents the range. Any outliers can be plotted independent of the box and whisker plot.
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This question is part of the following fields:
- Evidence Based Medicine
- Statistics
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Question 8
Incorrect
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What does the correlation coefficient r = 0 indicate with regards to linear relationships between two variables?
Your Answer:
Correct Answer: There is no correlation between two variables
Explanation:r = 0 if there is no correlation between two variables. The closer that r is to 0, the weaker the correlation.
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This question is part of the following fields:
- Evidence Based Medicine
- Statistics
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Question 9
Incorrect
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Regarding probability distribution, which of the following statements is CORRECT:
Your Answer:
Correct Answer: In a negative skew, the mass of distribution is concentrated on the right.
Explanation:Distribution of data is usually unimodal (one peak) but may be bimodal (two peaks) or uniform (no peaks, each value equally likely). The normal distribution is a symmetrical bell-shaped curve. The mean, median, and mode of a normal distribution are equal. In a positive skew, the right tail is longer and the mass of distribution is concentrated on the left; mean > median > mode. In a negative skew, the left tail is longer and the mass of distribution is concentrated on the right; mean < median < mode.
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This question is part of the following fields:
- Evidence Based Medicine
- Statistics
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Question 10
Incorrect
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What is the interquartile range of the following data set: 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 60, 70
Your Answer:
Correct Answer: 30
Explanation:5, 10, 15 /20, 25, 30 /35, 40, 45 /50, 60, 70Sample size (n) = 12Median = [(n+1)/2]th value = (12+1)/2 = 6.5 = halfway between 6th and 7th value = (30 +35)/2 = 32.5The lower (first) quartile = halfway between 15 and 20 = 17.5The upper (third) quartile = halfway between 45 and 50 = 47.5The interquartile range is the difference between the upper quartile and lower quartile = 47.5 – 17.5 = 30
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This question is part of the following fields:
- Evidence Based Medicine
- Statistics
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Question 11
Incorrect
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A new test is being developed to diagnose chlamydia. 1000 people aged 15 – 35 years attending a GUM clinic undergo the new test and the current gold standard nucleic acid amplification test (NAAT) to confirm the diagnosis. Of the 1000 people, 250 are diagnosed with chlamydia. Of the patients diagnosed with chlamydia, 240 test positive with the new diagnostic test and of the patients not diagnosed with chlamydia, 150 test positive with the new diagnostic test. What is the negative predictive value of this test:Chlamydia YesChlamydia NoTotalPositive testa= 240b = 150390Negative testc = 10d = 600610Total2507501000
Your Answer:
Correct Answer: 0.98
Explanation:Negative predictive value (NPV) is the proportion of individuals with a negative test result who do not have the disease.Negative predictive value (NPV) = d/(c+d) = 600/610 = 0.98 = 98%This means there is a 98% chance, if the test is negative, that the patient does not have chlamydia.
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This question is part of the following fields:
- Evidence Based Medicine
- Statistics
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Question 12
Incorrect
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Regarding likelihood ratios, which of the following statements is INCORRECT:
Your Answer:
Correct Answer: Likelihood ratios, like predictive values, are affected by the prevalence of the disease in the population.
Explanation:A likelihood ratio is a measure of the diagnostic value of a test. Likelihood ratios show how many times more likely patients with a disease are to have a particular test result than patients without the disease. Likelihood ratios are more useful than predictive values because they are calculated from sensitivity and specificity and therefore remain constant even when the prevalence of the disorder changes.
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This question is part of the following fields:
- Evidence Based Medicine
- Statistics
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Question 13
Incorrect
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Which of the following risk ratios indicates no difference in risk between two groups:
Your Answer:
Correct Answer: 1
Explanation:A risk ratio of 1 indicates no difference in risk between groups.If the risk ratio of an event is > 1, the rate of that event is increased in the exposed group compared to the control group.If the risk ratio is < 1, the rate of that event is reduced in the exposed group compared to the control group.
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This question is part of the following fields:
- Evidence Based Medicine
- Statistics
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Question 14
Incorrect
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A novel anti-tuberculosis medicine was compared to standard treatment and shown to cut the risk of death from 30 to 10 per 1000 people. How many patients would need to be treated (number need to treat (NNT)) in order to prevent ten additional tuberculosis deaths:
Your Answer:
Correct Answer: 500
Explanation:The risk of mortality in the control group (usual therapy) minus the risk of death in the treatment group equals the absolute risk reduction (ARR) of treatment.30/1000 minus 10/1000 = 20/1000 = 0.02NNT = 1/ARR = 1/0.02 = 50As a result, 50 people would need to be treated in order to prevent one additional fatality, and 500 people would need to be treated in order to avoid 10 additional deaths.
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This question is part of the following fields:
- Evidence Based Medicine
- Statistics
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Question 15
Incorrect
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A p value < 0.05 obtained from a study with a significance level (α) of 0.05, means all of the following, EXCEPT:
Your Answer:
Correct Answer: the result is clinically significant.
Explanation:A p value < 0.05:is statistically significantmeans that the probability of obtaining a given result by chance is less than 1 in 20means the null hypothesis is rejectedmeans there is evidence of an association between a variable and an outcomeNote that this does not tell us whether the result is clinically significant.
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This question is part of the following fields:
- Evidence Based Medicine
- Statistics
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Question 16
Incorrect
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A range of one standard deviation above and below the mean includes what approximate percentage of the sample values:
Your Answer:
Correct Answer: 0.68
Explanation:A range of one SD above and below the mean (+/- 1 SD) includes 68.2% of the sample values.A range of two SD above and below the mean (+/- 2 SD) includes 95.4% of the sample values.A range of three SD above and below the mean (+/- 3 SD) includes 99.7% of the sample values.
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This question is part of the following fields:
- Evidence Based Medicine
- Statistics
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Question 17
Incorrect
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A new blood test is being developed to diagnose DVT. 1000 people presenting to ED with suspected DVT undergo the new blood test and the gold standard doppler ultrasound to confirm the diagnosis. Of the 1000 people, 77 are confirmed to have a DVT. Of the patients diagnosed with DVT, 75 test positive with the new diagnostic test and of the patients not diagnosed with DVT, 125 test positive with the new diagnostic test. What is the negative predictive value of this test:DVT YesDVT NoTotalPositive testa= 75b = 125200Negative testc = 2d = 798800Total779231000
Your Answer:
Correct Answer: 0.99
Explanation:Negative predictive value (NPV) is the proportion of individuals with a negative test result who do not have the disease.Negative predictive value (NPV) = d/(c+d) = 798/800 = 0.99 = 99%This means there is a 99% chance, if the test is negative, that the patient does not have a DVT.
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This question is part of the following fields:
- Evidence Based Medicine
- Statistics
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Question 18
Incorrect
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Question 19
Incorrect
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Which of these is an example of ordinal data?
Your Answer:
Correct Answer: Disease staging system
Explanation:Categorical data or data that is ordered is Ordinal data e.g. disease staging system, pain scoring system.Disease staging system is the correct answer
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This question is part of the following fields:
- Evidence Based Medicine
- Statistics
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Question 20
Incorrect
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Regarding linear relationships between two variables, what does a positive correlation coefficient indicate:
Your Answer:
Correct Answer: The two variables are directly proportional
Explanation:A positive correlation coefficient means that the two variables are directly proportional e.g. height and weight in healthy growing children.
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This question is part of the following fields:
- Evidence Based Medicine
- Statistics
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SESSION STATS - PERFORMANCE PER SPECIALTY
