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• #### Question 1 - Which of the following risk ratios indicates no difference in risk between two groups:...

Incorrect

• Which of the following risk ratios indicates no difference in risk between two groups:

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.

• This question is part of the following fields:

• Evidence Based Medicine
• Statistics
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• #### Question 2 - Regarding linear relationships between two variables, what does a positive correlation coefficient indicate:...

Incorrect

• Regarding linear relationships between two variables, what does a positive correlation coefficient indicate:

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.

• This question is part of the following fields:

• Evidence Based Medicine
• Statistics
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• #### Question 3 - The weight distribution in a group of patients included in a study was...

Incorrect

• The weight distribution in a group of patients included in a study was normal. The patients averaged 80 kg in weight. 5 kg was determined to be the standard deviation. Which of the following statements most accurately describes this group of patients:

Correct Answer: 68% of the patients will weigh between 75 and 85 kg.

Explanation:

We can estimate the range of values that would be anticipated to include particular proportions of observations if we know the mean and standard deviation of a collection of normally distributed data: 68.2 percent of the sample results fall within a one SD range above and below the mean (+/- 1 SD), implying that 68 percent of the patients will weigh between 75 and 85 kg. Because +/- 2 SD encompasses 95.4 percent of the data, around 95 percent of the patients will weigh between 70 and 90 kg. +/- 3 SD encompasses 99.7% of the values, implying that nearly all of the patients will weigh between 65 and 95 kg.

• This question is part of the following fields:

• Evidence Based Medicine
• Statistics
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• #### Question 4 - Which of these is an example of ordinal data? ...

Incorrect

• Which of these is an example of ordinal data?

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

• This question is part of the following fields:

• Evidence Based Medicine
• Statistics
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• #### Question 5 - The interquartile range (IQ) is often displayed using which of the following: ...

Incorrect

• The interquartile range (IQ) is often displayed using which of the following:

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.

• This question is part of the following fields:

• Evidence Based Medicine
• Statistics
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• #### Question 6 - Which of the following is an example of continuous data: ...

Incorrect

• Which of the following is an example of continuous data:

Explanation:

Continuous data is data where there is no limitation on the numerical value that the variable can take e.g. weight, height.

• This question is part of the following fields:

• Evidence Based Medicine
• Statistics
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• #### Question 7 - A new blood test is being developed to diagnose DVT. 1000 people presenting...

Incorrect

• 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

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.

• This question is part of the following fields:

• Evidence Based Medicine
• Statistics
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• #### Question 8 - A new test is being developed to diagnose chlamydia. 1000 people aged 15...

Incorrect

• 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

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.

• This question is part of the following fields:

• Evidence Based Medicine
• Statistics
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• #### Question 9 - Regarding the power of a study, which of the following statements is INCORRECT:...

Incorrect

• Regarding the power of a study, which of the following statements is INCORRECT:

Correct Answer: The power of a study is not affected by data variability.

Explanation:

A study should only be undertaken if the power is at least 80%; a study power set at 80% accepts a likelihood of 1 in 5 (20%) of missing a statistically significant difference where one exists.The determinants of power are:the sample size (the power increases with sample size)the variability of the observations (the power increases as the variability decreases)the effect size of interest (the power is greater for a larger expected effect size)and the significance level, α (the power is greater if the significance level is larger); therefore the probability of a type I error increases as the probability of a type II error decreases.

• This question is part of the following fields:

• Evidence Based Medicine
• Statistics
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• #### Question 10 - Regarding relationships between two variables, what does a negative correlation coefficient indicate: ...

Incorrect

• Regarding relationships between two variables, what does a negative correlation coefficient indicate:

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.

• This question is part of the following fields:

• Evidence Based Medicine
• Statistics
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• #### Question 11 - The results from the study investigating the accuracy of a new diagnostic test can be...

Incorrect

• 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

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)

• This question is part of the following fields:

• Evidence Based Medicine
• Statistics
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• #### Question 12 - If the null hypothesis is wrongly rejected when it is actually true, this...

Incorrect

• If the null hypothesis is wrongly rejected when it is actually true, this is an example of:

Correct Answer: A test with a type I error

Explanation:

A type I error occurs when the null hypothesis is wrongly rejected when it is actually true and we conclude that there is a difference of effect when in reality there is none (a false positive result).

• This question is part of the following fields:

• Evidence Based Medicine
• Statistics
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• #### Question 13 - A type II error occurs when: ...

Incorrect

• A type II error occurs when:

Correct Answer: The null hypothesis is accepted when it is false.

Explanation:

A type II error occurs when the null hypothesis is wrongly accepted when it is actually false and we conclude that there is no evidence of a difference in effect when one really exists (a false negative result).

• This question is part of the following fields:

• Evidence Based Medicine
• Statistics
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• #### Question 14 - Which of the following best describes the positive predictive value of a diagnostic test:...

Incorrect

• Which of the following best describes the positive predictive value of a diagnostic test:

Correct Answer: The proportion of individuals with a positive test result who have the disease

Explanation:

Positive predictive value (PPV) is the proportion of individuals with a positive test result who actually have the disease.PPV = a/(a+b)

• This question is part of the following fields:

• Evidence Based Medicine
• Statistics
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• #### Question 15 - Which of the following is an example of discrete data: ...

Incorrect

• Which of the following is an example of discrete data:

Explanation:

Discrete data is quantitative data that can only take whole numerical values e.g. number of children, number of days missed from work.

• This question is part of the following fields:

• Evidence Based Medicine
• Statistics
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• #### Question 16 - Which of the following is an example of a non-parametric test: ...

Incorrect

• Which of the following is an example of a non-parametric test:

Correct Answer: All of the above

Explanation:

All of the above answers are non-parametric tests.

• This question is part of the following fields:

• Evidence Based Medicine
• Statistics
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• #### Question 17 - A new chemotherapy drug is being tested. The intervention reduces the risk of...

Incorrect

• A new chemotherapy drug is being tested. The intervention reduces the risk of death from 10 in 1000 to 5 in 1000. What is the number needed to treat to prevent one death:

Explanation:

Absolute risk reduction (ARR) of treatment = risk of death in control group – risk of death in treatment groupARR = (10/1000) – (5/1000) = 5/1000 = 0.005Number needed to treat (NNT) = 1/ARR = 1/0.005 = 200Therefore 200 people would need to be treated to prevent one extra death.

• This question is part of the following fields:

• Evidence Based Medicine
• Statistics
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• #### Question 18 - What is the interquartile range for these numbers: 11, 4, 6, 8, 3,...

Incorrect

• What is the interquartile range for these numbers: 11, 4, 6, 8, 3, 10, 8, 10, 4, 12, 31?

Explanation:

We obtain 3, 4, 4, 6, 8, 8, 10, 11, 12, and 31, and sample size (n) = 11 when we order the data. [(n+1)/2] = median 6th value = (11+1)/2 = [(n+1)/4] represents the bottom (first) quartile. (3rd value = 4th value = (11 + 1)/4 3[(n+1)/4] for the top (third) quartile 3[(11 + 1)/4] = 9th value = 11th value = 11th value = 11th value = 11th value = 11th value = 11th value = 11th value = 11th The difference between the upper and lower quartiles is the interquartile range, which is equal to 11 minus 4 = 7.

• This question is part of the following fields:

• Evidence Based Medicine
• Statistics
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• #### Question 19 - A new blood test is being developed to diagnose DVT. 1000 people presenting...

Incorrect

• 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 positive predictive value of this test:DVT YesDVT NoTotalPositive testa= 75b = 125200Negative testc = 2d = 798800Total779231000

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) = 75/200= 0.375 = 37.5%This means there is a 37.5% chance, if the test is positive, that the patient actually has a DVT.

• This question is part of the following fields:

• Evidence Based Medicine
• Statistics
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• #### Question 20 - A novel anti-tuberculosis medicine was compared to standard treatment and shown to cut...

Incorrect

• 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:

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.

• This question is part of the following fields:

• Evidence Based Medicine
• Statistics
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• #### Question 21 - A new test is being developed to diagnose chlamydia. 1000 people aged 15...

Incorrect

• 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

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.

• This question is part of the following fields:

• Evidence Based Medicine
• Statistics
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• #### Question 22 - Which of the following data types does a pain-scoring system represent? ...

Incorrect

• Which of the following data types does a pain-scoring system represent?

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.

• This question is part of the following fields:

• Evidence Based Medicine
• Statistics
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• #### Question 23 - Which of the following terms describes the proportion of individuals with a negative...

Incorrect

• Which of the following terms describes the proportion of individuals with a negative test result who actually do not have a disease:

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)

• This question is part of the following fields:

• Evidence Based Medicine
• Statistics
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• #### Question 24 - A range of one standard deviation above and below the mean includes what...

Incorrect

• A range of one standard deviation above and below the mean includes what approximate percentage of the sample values:

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.

• This question is part of the following fields:

• Evidence Based Medicine
• Statistics
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• #### Question 25 - What does the correlation coefficient r = 0 indicate with regards to linear...

Incorrect

• What does the correlation coefficient r = 0 indicate with regards to linear relationships between two variables?

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.

• This question is part of the following fields:

• Evidence Based Medicine
• Statistics
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• #### Question 26 - Regarding likelihood ratios, which of the following statements is INCORRECT: ...

Incorrect

• Regarding likelihood ratios, which of the following statements is INCORRECT:

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.

• This question is part of the following fields:

• Evidence Based Medicine
• Statistics
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• #### Question 27 - What is the interquartile range of the following data set: 5, 10, 15,...

Incorrect

• What is the interquartile range of the following data set: 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 60, 70

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

• This question is part of the following fields:

• Evidence Based Medicine
• Statistics
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• #### Question 28 - The results from the study investigating the accuracy of a new diagnostic test can be...

Incorrect

• 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

Explanation:

Positive predictive value (PPV) is the proportion of individuals with a positive test result who actually have the disease.PPV = a/(a+b)

• This question is part of the following fields:

• Evidence Based Medicine
• Statistics
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• #### Question 29 - A p value < 0.05 obtained from a study with a significance level...

Incorrect

• A p value < 0.05 obtained from a study with a significance level (α) of 0.05, means all of the following, EXCEPT:

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.

• This question is part of the following fields:

• Evidence Based Medicine
• Statistics
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• #### Question 30 - Regarding probability distribution, which of the following statements is CORRECT: ...

Incorrect

• Regarding probability distribution, which of the following statements is CORRECT:

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.

• This question is part of the following fields:

• Evidence Based Medicine
• Statistics
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