Question 1Using this 2 x 2 table, determine which of the following.pdf
- 1. Question 1 Using this 2 x 2 table, determine which of the following is the correct odds ratio. Exposure to variable of interest Existence of Disease designated as case (yes disease) or control (no) Case Control Yes exposed 27 23 50 No not exposed 20 24 44 Total 47 47 94 Answer 3.4 .54 .96 1.4 Question 2 . Which of the following statements about cumulative incidence and/or incidence density is true? Answer Incident density is also called the incidence rate. Both the incidence density and the cumulative incidence use number of people at risk for disease in the denominator, though their numerators are different. The numerator for incidence density is calculated in person-years. Cumulative incidence is usually larger than incidence density since the denominator is smaller. 1 points Question 3 1. Which of the following statements about prevalence and/or incidence is true? Answer You need to know the number of people at risk at the beginning of the year to calculate the prevalence. Incidence is based on a sample, while prevalence is based on a population. Prevalence is an estimate of the true incidence of disease in a population. You need to know the number of people at risk at the beginning of the year to calculate the cumulative incidence for that year. Question 4
- 2. Using this table, which of the following is the incidence density of whooping cough in year 2 in the population that was sampled, given that there were 190 people at risk after year 1? Number diagnosed When diagnosed Multiplier based on time of diagnosis Total Person-Years 2 1st quarter .25 .5 4 2nd quarter .50 2 3 3rd quarter .75 2.25 9 4.75 (Hint: Number left contributing 1 person year each is 190 ? 9 = 181) Answer .4% 4.8% .5% 1.9% Question 5 Using this 2 x 2 table, determine which of the following is the correct odds ratio. Exposure to variable of interest Existence of Disease designated as case (yes disease) or control (no) Case Control Yes exposed 34 29 63 No not exposed 31 36 67 Total 65 65 130 Answer .8 1.4 3.8 .5 Question 6 Using these numbers, which of the following is the cumulative incidence in year 2 of flu in the population that was sampled? Year Number at Risk New Cases 1 250 34 2 250 47
- 3. Answer 14% 19% 16% 8% Question 7 1. Using these numbers, which of the following is the prevalence of smoking in the population that was sampled? Total number respondents: 80,000 Number of respondents who smoke: 14,243 Answer .2 .17% 17% 7% 1 points Question 8 1. Which of the following statements about cumulative incidence and/or incidence density is true? Answer You cannot calculate either incidence density or cumulative incidence using a sample; you must use the whole population. Incidence density can be calculated using a sample but cumulative incidence cannot. Both incidence density and cumulative incidence can be calculated using a sample of the population. Both types of incidence are parameters, whereas prevalence is a statistic. 1 points Question 9 1. Using this 2 x 2 table, determine which of the following is the correct risk ratio. Exposure to variable of interest Existence of Disease designated (yes disease) or (no disease) Yes No Yes exposed 52 14 66
- 4. No not exposed 12 82 94 Total 64 96 160 Answer 6 5.6 .8 3 Question 10 Which of the following statements about prevalence and/or incidence is true? Answer The numerator for incidence and prevalence is the number of people with the disease at the end of the year. The numerators for both incidence and prevalence are the same, only the denominators are different. The numerator for incidence is the number of new cases diagnosed in a given period of time. The numerator for incidence is always the number of new cases diagnosed in a year. Question 11 Using these numbers, which of the following is the prevalence of diabetes in the population that was sampled? Total number respondents: 245,000 Number of respondents diagnosed with diabetes: 27,346 Answer 11% 1.1% 1.2% .11% Question 12 Which of the following statements about prevalence and/or incidence is true? Answer Incidence is an estimate and prevalence is a parameter.
- 5. Incidence is based on new cases. Incidence is an estimate of the prevalence of disease. None are true. Question 13 Which of the following is the correct interpretation of a prevalence of 5%? Answer There were 5 new cases diagnosed in the past year. There were 5 new cases diagnosed per 100 people at risk. There were 5 new cases diagnosed per 100 people in the sample. There are 5 people with the disease in a sample of 100 people. Question 14 Which of the following is the correct interpretation of an incident density of 5%? Answer There were 5 new cases diagnosed in the past year. There were 5 new cases diagnosed per 100 person-time years of people at risk. There were 5 new cases diagnosed per 100 people in the sample. There are 5 people with the disease in a sample of 100 people. Question 15 1. Using these numbers, complete the following table. What is the value for "a" in the table: Number diagnosed When diagnosed Multiplier based on time of diagnosis Total Person-Years 6 1st quarter .25 4 2nd quarter .50 8 3rd quarter .75 18 "a" Answer 18 9.5 6
- 6. 1.5 Question 16 Which of the following is the correct interpretation of a cumulative incidence of 5%? Answer None are true. There were 5 new cases diagnosed per 100 person-time years. There were 5 new cases diagnosed per 100 people at risk. There are 5 people with the disease in a sample of 100 people. Question 17 Using these numbers, which of the following is the cumulative incidence in year 2 of lung cancer in the population that was sampled? Year Number Sampled Total Cases at end of the year 1 50 4 2 50 8 Answer 8% 16% .8% 1.6% Question 18 Which of the following is the correct interpretation of an odds ratio of 2.9? Answer The odds of a disease given a specific exposure are 2.9 times the odds of disease without that exposure. There are 2.9 people per year diagnosed with a given disease. If 100 people are exposed to a risk factor for a disease, 2.9 people will get the disease in 1 year. The odds of a disease given no exposure to risk are 2.9 times the odds of disease given exposure to risk. Question 19 Which of the following is true about the difference between an odds ratio and a risk ratio? Answer The odds ratio requires you to know the true prevalence of a disease.
- 7. The risk ratio is the best formula to use with Case-Control studies. The odds ratio works best with Case-Control studies. You can use either the odds ratio or the risk ratio with Case-Control studies, as the result will be the same with both. Question 20 Which of the following is true about the difference between an odds ratio and a risk ratio? Answer The odds ratio is always higher than the risk ratio. It is always best to use the odds ratio, if possible. The odds ratio is a good estimate of the risk ratio when the risk ratio is less than 10. The odds ratio is a good estimate of the risk ratio when the disease being studied is rare. Solution 1 3.4 2 Both the incidence density and the cumulative incidence use number of people at risk for disease in the denominator, though their numerators are different. 3 Incidence is based on a sample, while prevalence is based on a population. 4 4.8% 5 1.4
- 8. 6 19% 7 17% 8 Incidence density can be calculated using a sample but cumulative incidence cannot. 9 5.6 10 The numerators for both incidence and prevalence are the same, only the denominators are different. 11 1.2% 12 Incidence is an estimate of the prevalence of disease. 13 There were 5 new cases diagnosed per 100 people in the sample. 14 There were 5 new cases diagnosed per 100 people in the sample.
- 9. 15 9.5 16 There were 5 new cases diagnosed per 100 person-time years. 17 16% 18 There are 2.9 people per year diagnosed with a given disease. 19 The odds ratio works best with Case-Control studies. 20 The odds ratio is a good estimate of the risk ratio when the disease being studied is rare.