30— Length bias occurs because fast growing tumors are more likely to be picked up by a screening test tan are slow growing tumors. True False  31— Selection bias is most likely to occur in studies where Only exposure has occurred at the time of subject selection Only outcome has occurred at the time of subject selection Exposure and outcome have already occurend at the time of subject selection 32—- Read the following abstract by lee YC, Chien KL, Chen HH, Lifestyle risk factors associated with fatigue in graduate students. J Formos Med Assoc. 2007 Jul; 106(7): 565-72 National Taiwan University, Taipe, Taiwan. Background/Purpose: Fatigue is not only common in clinical patients but is also prevalent in the healthy population. This student aimed to estimate the prevalence rate of fatigue and identify significant risk factors among graduate students. METHODS : Health check-ups were carried out on graduate student who were newly admitted to the National Taiwan University in thi cross- sectional study. A total of 1806 attendees (response rate 84%) agreed to participate in the fatigue survey, which used the Checklist Individual Strength questtionarie (CIS 20). The modiefd Baecke´s questionnaire was used to quantify the intensity of physical activity. RESULTS: The prevalence rates of fatigue were 45.8% for males and 48.9% for females. Regulars meals (odds ratio [OR], 0.69) and exercise habits (OR, 0.68), insomnia (OR, 2.23), greater amount of sleeping time (OR, 0.7), identity (doctorate vs. Master students; OR, 0,61) and chronic disease history (OR, 1,61) were statistically significant predictors for fatigue. Intensity of physical activity was protective factor (ORs, 0,72, 0,50 and 0,36 in the 2nd, 3rd and top quartiles vs. 1 st quartille; p 0.0001). CONCLUSION: A high prevalence rate of fatigue among the graduate students was demostrated. The risk factors among young adults are not only relatad to corrent chronic diseade and insommia but are also attributed to the lack of physical activity. When we talk about the results of this study bieng relevant to the etiologic role that lifestyle factors may play in the etiology f tatigue among graduate students, as opposed to the role they may play among the general population at large, we are referring to: Confounding Effect-modification External validity Internal validity 33—– A public health group conducts blood glucosa screenings at a local shopping center. Individuals whose results fall beyond a certain cut point are referred for further testing. This is an example of: Diagnostic testing Primary prevention Secondary prevetion Tertiary prevention 34—– In setting the cut point for a screening test to be considered positive, what will happen if the cutpoint is set too low (assuming a highert score is more indicative of tru disease presence)? The sensitivity will increase and specificity will decrease The sensitivity will decrease and the specificity will increase Both the sensitivity and the specificity will increase Both the sensitivity and specificity will decrease 35—– Removing a precancerous lesión on the skin as to prevent skin cáncer Primary Prevention Secondary Prevention Tertiary Prevention 36———- What type of epidemic is caracterizad by person-to-person transmission that often results in an epidemic curve with two or more modes? Continuing epidemic Intermittent epidemic Poin Source epidemic Propagated epidemic 37— Chavarro et al (2008) reportd: ¨we examined the relation of fish and seafood n-3 fatty acid intakes with prostate cáncer incidence and mortality. During 382,144 person-years of follow-up. 2,161 men were diagnosed with prostate cáncer and 230 died of prostate cáncer. In crude analyses, seafood n-3 fatty acid intake was associated with prostate cance mortality (p 0,02). Base don this information, what can you conclude? The association between n-3 fatty acid intake and prostate cáncer mortality is highly valid. The association between n-3 fatty acid intake and prostate cáncer mortality is unlikely to be due to bias The association between n-3 fatty acid intake and prostate cáncer mortality is unlikely to be due to chance The association between n-3 fatty acid intake and prostate cáncer mortality is unlikely to be due to confounding 38—- Endemic means that a disease Occurs clearly in excess of normal expectancy Is habitually present in human popullyations Affects a large number of countries simultaneously Exhibits a seasonal pattern 39 —Selection bias is most likely to occurs in studies where Only exposure has occurred at the time of subject selection Only outcome has occured at the time of subject selection Exposure and outcome have already occured at the time of subject selection 40 ——The most important criterion for establishing causality is Eliminating chance, bias and confounding Searching for effect-modification Having experimental evidence of biologic plausibility Correct temporal sequence.

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