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Relative Risk Calculations Worksheet
Guidelines & Grading Rubric
Purpose
The purpose of this assignment is to help you to begin to understand and apply the important counts, ratios, and statistics presented in healthcare and epidemiological research. Remember to use the list of formulas presented prior to the problems and to carefully consider the purpose of each calculation and how it is interpreted.
Course Outcomes
Through this assignment, the student will demonstrate the ability to:
(CO #3) Identify appropriate outcome measures and study designs applicable to epidemiological subfields such as infectious disease, chronic disease, environmental exposures, reproductive health, and genetics.
(CO #4) Apply commonly used measures of health risk.
(CO #6) Identify important sources of epidemiological data.
Due Date: Sunday 11:59 p.m. (MT) at the end of Week 3
Total Points Possible: 50
REQUIREMENTS:
1. Complete the Risk Calculation Worksheet located in DocSharing.
2. For each question identify the correct answer.
3. Submit the worksheet to the DropBox by 11:59 p.m. MT Sunday of Week 3
Epidemiological Formulas and Statistics
Parameter Definition Formula
Incidence (exposed) Incidence of new cases of disease in persons who were exposed number (exposed with disease)/Total number of exposed
Incidence (unexposed) Incidence of new cases of disease in persons who were not exposed number (unexposed with disease)/Total number of unexposed
Incidence of Disease Measure of risk. Total number in a population with a disease divided by the total number of the population. Number with the disease/ Total population number
Relative Risk Risk of disease in one group versus another. Risk of developing a disease after exposure. If this number is one, it means there is no risk. R(exposed)/Risk (unexposed) (# exposed with disease(divided by)/total of all exposed)
(# of non-exposed with disease/(divided by)total of all non exposed)
Odds Ratio A measure of exposure and disease outcome commonly used in case control studies. R(exposed) / R (unexposed)
1- R(exposed) 1-R(unexposed)
Prevalence The number of cases of a disease in a given time regardless of when it began. (new and old cases) (Persons with the disease/ Total population) X 1000
Attributable Risk The difference in disease in those exposed and unexposed and is calculated from prospective data. Directly attributed to exposure (if exposure gone, disease would be gone) R(exposed) – R(unexposed)
Crude Birth Rate The number of live births per 1,000 people in the population (# of births/estimated mid-year population) X 1000
Crude Death Rate The number of deaths per 1,000 people in the population (# of deaths/estimated mid-year population) X 1000
Fetal Death Rate The number of fetal deaths (20 weeks or more gestation) per 1,000 live births. (# of fetal deaths/ # of live births + fetal deaths) X 1000
Annual Mortality Rate Usually an expression of a specific disease or can be all causes per 1,000 people for a year. (# of deaths of all causes (or a specific disease)/Mid-year population) X 1000
Case Fatality Rate The parentage of individuals who have a specific disease and die within a specific time after diagnosis. (# of persons dying from a disease after diagnosis or set period/ # of persons with the disease) X 100
Relative Risk Calculation Worksheet Answer Key
Prior to completing this worksheet, review the lessons, reading and course text up to this point. Also review the tables of calculations. Each question is worth five (5) points. There is only one right answer for each of the ten problems.
1. The population in the city of Springfield, Missouri in March, 2014 was 200,000.
The number of new cases of HIV was 28 between January 1 and June 30th 2014.
The number of current HIV cases was 130 between January 1 and June 30th 2014.
The incidence rate of HIV cases for this 6 month period was:
A. 7 per 100,000 population
B. 14 per 100,000 population
C. 28 per 100,000 population
D. 85 per 100,000 population
2. The prevalence rate of HIV cases in Springfield, Missouri as of June 30, 2014 was:
A. 14 per 100,000 population
B. 28 per 100,000 population
C. 79 per 100,000 population
D. 130 per 100,000 population
3. In a North African country with a population of 5 million people, 50,000 deaths occurred during 2014. These deaths included 5,000 people from malaria out of 10,000 persons who had Malaria.
What was the total Annual Mortality Rate for 2014 for this country? (please show your work)
(# of deaths of all causes (or a specific disease)/Mid-year population) X 1000
25,000/2.5 million (0.01) x 1000=10
4. What was the cause-specific mortality rate from malaria? (please show your work)
(# of deaths of all causes (or a specific disease)/Mid-year population) X 1000
2500/5000 (0.5) x 1000 = 500
5. What was the case-fatality percent from malaria?
(# of persons dying from a disease after diagnosis or set period/ # of persons with the disease) X 100
5000/10000 (0.5) x 100 = 50
6. Fill in and total the 4 X 4 table for the following disease parameters:
Total number of people with lung cancer in a given population = 120
Total number of people with lung cancer who smoked = 90
Total number of people with lung cancer who did not smoke = 30
Total number of people who smoked = 150
Total number of people in the population = 350
Fill in the missing parameters based on the above.
YES LUNG CANCER
NO LUNG CANCER TOTALS
YES SMOKING
90 60 150
NO SMOKING
30 170 200
TOTALS
120 230 350
7. From Question 6, what is the total number of people with no lung cancer?
230
8. From question 6, what is the total number of people who smoked, but did not have lung cancer?
60
9. Set up the problem for relative risk based on the table in #6.
(# exposed with disease (divided by)/total of all exposed)
(# of non-exposed with disease/ (divided by) total of all non-exposed)
90/150
30/200
10. Calculate the relative risk.
0.6
0.005 =120
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