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Question 1
Incorrect
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Which of the following statements is true regarding box plots?
Your Answer: Should be used for numerical and not categorical outcomes
Correct Answer: Show distributionally outlying values and provide data summaries that are not unduly influenced by those outliers
Explanation:Box plots can be used to display numerical outcomes and give valid summaries (median and interquartile range or IQR) for any distributional form that the outcomes might take. Additionally, they show outlying values and provide data summaries that are not unduly influenced by those outliersOther options:- The box itself represents the interquartile range, with the two whiskers representing the variability outside the upper and lower quartiles.- Variability is represented with whiskers and feathers are used in fan charts.They are not as informative as showing the actual values but can be used to make comparisons of medians and IQRs between subgroups.
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This question is part of the following fields:
- Epidemiology And Statistics
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Question 2
Correct
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A study of 500 men shows a significant correlation between their blood pressures and weights (r = 0.45, P = 0.0014).Which one of the following is true?
Your Answer: There is a linear tendency for heavier men to have higher blood pressures
Explanation:The main result of a correlation is called the correlation coefficient (or r). It ranges from -1.0 to +1.0. The closer r is to +1 or -1, the more closely the two variables are related.If r is close to 0, it means there is no relationship between the variables. If r is positive, it means that as one variable gets larger the other gets larger. If r is negative it means that as one gets larger, the other gets smaller (often called an inverse correlation).
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This question is part of the following fields:
- Epidemiology And Statistics
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Question 3
Correct
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A cohort study is developed to assess the correlation between blood pressure and working long hours. After 10 years of follow-up and for the 1050 individuals working less than 40 hours per week, 1000 patients had normal blood pressure and 50 patients were diagnosed with hypertension. For the 660 patients working more than 40 hours per week, 600 patients had normal blood pressure and 60 patients were diagnosed with hypertension. If you work more than 40 hours per week, what is the odds ratio of developing hypertension compared to the individuals working less than 40 hours per week?
Your Answer: 2
Explanation:An odds ratio (OR) is a measure of the association between an exposure and an outcome. The OR represents the odds that an outcome will occur given a particular exposure, compared to the odds of the outcome occurring in the absence of that exposure. Odds ratios are most commonly used in case-control studies, however they can also be used in cross-sectional and cohort study designs as well (with some modifications and/or assumptions). Wherea = Number of exposed casesb = Number of exposed non-casesc = Number of unexposed casesd = Number of unexposed non-casesOR=(a/c) / (b/d) = ad/bc
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This question is part of the following fields:
- Epidemiology And Statistics
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Question 4
Correct
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Which of the following is true in logistic regression analysis?
Your Answer: Yields adjusted odds ratios
Explanation:Logistic regression analysis is an easy to use regression that can serve to estimate how a binary or dichotomous dependent variable, for example whether or not a student passes or fails a medical exam, is related to the number of hours the student studies for the exam. This regression is able to yield an odds ratio, i.e. the probability of passing the exam based on each additional hour of study. As stated, the outcome does not need to be normally distributed but is usually binary. This type of analysis is not complex and does not need to be avoided as it is available most statistical packages.
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This question is part of the following fields:
- Epidemiology And Statistics
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Question 5
Correct
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In a study, 50 out of 100 smokers developed lung cancers and 50 out of 200 non-smokers developed lung cancers. Which of the following is accurate?
Your Answer: Relative risk=2
Explanation:Relative risk = (Incidence in exposed group)/incidence in unexposed group). So in this case RR = (50/100)/(50/200) = 2.
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This question is part of the following fields:
- Epidemiology And Statistics
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Question 6
Incorrect
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According to a cross-sectional survey of >500 subjects, an estimated 10% of a group of children that have a sibling with severe eczema, have asthma. On the other hand, only 0.5% without a sibling with severe eczema have asthma. You want to test the difference of 9.5% for significance. Which of the following tests would you use?
Your Answer: Chi-square
Correct Answer: Fisher’s exact test
Explanation:To quantify differences between percentages you can use Fisher’s exact test.Odds ratios, relative risks and number needed to treat are ways of quantifying differences between percentages in two groups, however are not in themselves significance tests.
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This question is part of the following fields:
- Epidemiology And Statistics
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Question 7
Correct
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Which of the following best describes odds ratios?
Your Answer: The odds of an event in one group divided by the odds of the event in another
Explanation:Odds ratios are best described as the odds of an event in one group divided by the odds of the event in another. They form an alternative to the relative risk in case–control studies and are close to the relative risk when events are rare. The odds are the number of the event divided by the number without the event, which is less intuitive than the risk, which is the number with the event divided by the total. Odds ratios are therefore less intuitive than relative risks. Logistic regression analysis outputs variable coefficients which are the log of the odds ratio.
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This question is part of the following fields:
- Epidemiology And Statistics
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Question 8
Incorrect
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For a given condition, disease or attribute, there will be a proportion of people in a population who have it at a specified point in time or over a specified period of time. Which of following is the best term which describes the above?
Your Answer: Incidence
Correct Answer: Prevalence
Explanation:Prevalence:
This is the proportion of individuals in a population who have a specific condition, disease, or attribute at a given point in time or over a specific period.
Incidence:
This is the number of new cases of a specific condition, disease, or attribute that develop in a population during a specified period of time.
Specificity:
This refers to the ability of a test to correctly identify those without the condition (true negative rate).
Sensitivity:
This refers to the ability of a test to correctly identify those with the condition (true positive rate).
Probability:
This is a measure of the likelihood that an event will occur. In the context of diseases, it can refer to the likelihood of developing a condition.
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This question is part of the following fields:
- Epidemiology And Statistics
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Question 9
Correct
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The following is true of power calculations for comparison of a numerical measurement between the two groups:
Your Answer: Should be performed before the study commences
Explanation:Power calculations are a important step in study design and preparation, but do not directly help with the interpretation of the results. They are used to determine how many subjects are needed in order to avoid errors in accepting or rejecting the null hypothesis. These calculations are not usually complex and for the best results, the power of the test should be set to above 80%.
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This question is part of the following fields:
- Epidemiology And Statistics
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Question 10
Correct
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In a trial for a new treatment of lung disease, a traditional regime was given to 130 patients, 30 of whom died, while the new treatment was given to 125 patients, 20 of whom died. Which of the following tools will be useful in calculating whether the above results are due to chance?
Your Answer: Chi-squared analysis
Explanation:The Chi squared test is used to find the relationship between two variables, determining whether they are not independent of each other. This test of statistical significance allows you to determine the degree of confidence with which you can accept or reject the null hypothesis. The student t test compares the significant differences in data means, while rank correlation, linear regression and the correlation coefficient all help to measure the linear relationship between variables.
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This question is part of the following fields:
- Epidemiology And Statistics
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SESSION STATS - PERFORMANCE PER SPECIALTY
