whooping cough

Instructions:

mk1985 posted a question Apr 05, 2014 at 10:46pm

Question 1

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 2

Which of the following statements about cumulative incidence and/or incidence density is true?

Answer

The formula for cumulative incidence is the number of new cases divided by the number at risk in person-time years.

The formula for incidence density is the number of new cases divided by the number at risk in person-time years.

The formula for incidence density is the number of existing cases divided by the number at risk in person-time years.

The formula for cumulative incidence is the number of existing cases divided by the number at risk in person-time years.

Question 3

Using this table, which of the following is the incidence density of lung cancer 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

4 1st quarter .25 1

12 2nd quarter .50 6

6 3rd quarter .75 4.5

22 11.5

(Hint: Number left contributing 1 person year each is 190 ? 22 = 168)

Answer

12%

5%

1.9%

11.5%

Question 4

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

No not exposed 12 82 94

Total 64 96 160

Answer

6

5.6

.8

3

Question 5

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%

Question 6

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 7

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 8

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 9

Using these numbers, which of the following is the prevalence of heart disease in the population that was sampled?

Total number respondents: 345,000

Number of respondents diagnosed with heart disease: 49,999

Answer

5%

.14%

1.4%

14%

Question 10

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 34 17 51

No not exposed 24 27 51

Total 58 44 102

Answer

2.2

1.4

3

.7

Question 11

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

Answer

14%

19%

16%

8%

Question 12

Using these numbers, which of the following is the cumulative incidence in year 1 of breast cancer in the population that was sampled?

Year Number at Risk New Cases

1 240 22

2 240 16

Answer

9%

6%

8%

.8%

Question 13

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.

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 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

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

1.5

Question 16

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 17

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 18

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 19

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 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.