Exam questions in Statistics and Evidence-based medicine, June 2014 2. sem. Medis/Medicin, Modul 2.4. “Statistics”: ESSAY-TYPE QUESTION 1. A case-control study was conducted among men aged 40-70 years in order to determine whether exposure to risk factor X increases the likelihood of heart attack. The case group was comprised of 6 men who had recently had a heart attack. Among the cases, 5 reported that they were exposed to the risk factor X prior to their heart attack. The control group was comprised of 5 individuals who never had a heart attack. Among the controls, one person reported exposure to the risk factor X. Questions: a) Set up the two by two table for these data. b) Calculate the odds ratio (OR) for exposure to risk factor X among those with heart attack compared to those without heart attack. Interpret the result and make a conclusion on association of exposure to risk factor X and heart attack. c) Calculate the 95% confidence interval for the OR in (b). Interpret the result and make a conclusion on association of exposure to risk factor X and heart attack. d) Imagine, that the table in (a) contains the results of a cohort study. Calculate the risk ratio (RR) for heart attack among those who were exposed to risk factor X compared to those who were not exposed to risk factor X. Interpret the result and make a conclusion on association of exposure to risk factor X and heart attack. e) Would a randomized controlled trial be a good choice for a study to determine whether exposure to a risk factor increases the likelihood of heart attack in men aged 40-70 years? Why or why not? Max point: 33 Achieved point: TRUE OR FALSE QUESTION 2. Indicate whether the statement is true or false. A ’Temporal relationship’ is one of the Bradford Hill’s criteria for causation. B In a case-control study to investigate whether eczema in children is related to cigarette smoking by their parents, parents would be randomly allocated to smoking and non-smoking groups. Max point: 2 Achieved point: 1 ESSAY-TYPE QUESTION 3. Fourteen different second-year medical students took blood pressure measurements of the same patient and the results are listed below. (SBP= Systolic Blood Pressure; DBP= Diastolic Blood Pressure) SBP DBP 138 82 130 91 135 100 140 100 SBP DBP 143 105 140 85 130 70 150 100 120 80 125 90 120 80 130 80 130 80 144 98 Questions a) Make a scatterplot of SBP versus DBP; b) Calculate the correlation coefficient between SBP and DBP; c) Comment on the nature and strength of any association between the two variables; d) Is this association statistically significant? e) Apart from correlation, does the data suggest other important issues that might be interesting to address? Max point: 21 Achieved point: ESSAY-TYPE QUESTION 4. The following data are the lengths of the menstrual cycle in a random sample of 15 women: 26, 24, 29, 33, 25, 26, 23, 30, 31, 30, 28, 27, 29, 26, 28 (days) Questions: a) Using a statistical software (e.g., SPSS), calculate following sample characteristics: mean, median, range, variance, standard deviation and standard error of the mean; b) Is the distribution of the lengths normal? (How did you check that?) c) If the distribution of the lengths is assumed to be normal, what formula is appropriate to be used to calculate a 95% confidence interval (CI) for the population mean length? d) Using this formula, calculate a 95% CI for the population mean length and explain the result. e) Using a statistical software (e.g., SPSS), calculate a 95% CI for the population mean length. f) Are the results in (d) and (e) similar or different? Why? Max point: 29 Achieved point: 2 ”Evidens”: EXTENDED MATCHING 5. Evidens Begreber: A. De epidemiologiske metoderegler B. Evidensbaseret medicin og praksis C. Evidensbaseret viden D. Systematiske reviews af kohorte-studier E. Systematiske reviews af RCT F Systematiske reviews af case-control studier Opgave: Vælg fra listen af begreber det, der passer bedst til hvert af de nedenstående udsagn. Viden af høj kvalitet i forhold til de epidemiologiske metoderegler Danner grundlag for udarbejdelse af tjeklister til bedømmelse af kvaliteten af egne- og andres studier Befinder sig på det højeste evidensniveau i Oxford Centre for EvidenceBased Medicine’s skema til graduering af evidensen i epidemiologiske undersøgelser Anvendelse af evidensbaseret viden (hvor en sådan findes) som basis for Sundhedsvæsenets tilbud/ydelser Har D, E eller F den laveste grad af evidens i forhold til evidenshierarkiet? Knytter epidemiologi, statistik og evidens sammen Er kliniske ekspertise integreret med den bedst tilgængelige kliniske evidens fundet ved systematisk litteratursøgning Max point: 5 Opnåede point MULTIPLE CHOICE OPGAVE 6. Hvad afgør hvor i evidenshierarkiet en undersøgelse placeres? A Formålet med undersøgelsen B Undersøgelses-designet C Størrelsen af stikprøven, der indgår i undersøgelsen D Reliabiliteten E Graden af generaliserbarhed Max point 3 Opnåede point 3 EXTENDED MATCHING 7. Evidens Begreber: A. STROBE B. PRISMA C. CASP Opgave: Vælg fra listen af begreber det, der passer bedst til hvert af de nedenstående udsagn. Tjekliste til vurdering af RCT Tjekliste til vurdering af undersøgelser, der indeholder både statistiske, organisatoriske og økonomiske overvejelser Tjekliste til vurdering af Systematic Reviews and Metanalyser Tjekliste til vurdering af undersøgelser, der er baseret på et eksperimentelt design Tjekliste til vurdering af observationelle epidemiologiske studier Tjekliste til vurdering af undersøgelser, der er baseret på et observationelt design Max point: 4 Opnåede point MULTIPLE CHOICE OPGAVE 8. Evidens forsøges i dag indført i praksis gennem en række tiltag. Hvilken af nedenstående er IKKE korrekt? A Sundhedsfagligt indhold i elektroniske patientjournaler B Map of medicine C Telecare-Nord D Den danske kvalitetsmodel E E-dok i Region Midt Max point 3 Opnåede point 4
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