# Epidemiology chp 2

 Data cleaning -the review of data for accuracy and completeness -A clean data set contains a group of data that are ready for coding and analysis Bar Chart •Is a type of graph that shows the frequency of cases for categories of a categorical (discrete) variable such as a Yes/No variable. Histogram a similar chart to bar chart, used for continuous variables Continuous Variable -A variable that could have an infinite number of values along a continuum. -Ex. height, weight, and blood sugar level-Cannot be anwsered with yes/no Line Graph -Used to display trends, e.g., time trends Pie Chart A circle that shows the proportion of cases according to several categories Ratio The value obtained by dividing one quantity by another.Examples are: Rates Proportions Percentages Ratio Calculation With respect to AIDS mortality, the sex ratio of deaths (male to female deaths) = X/Y, where: ─X= 450,451 ─Y= 89,895 The sex ratio = 450,451/ 89,895 = 5 to 1 (approximately). Proportion •A type of ratio in which the numerator is part of the denominator •May be expressed as a percentage Percentage •A proportion that has been multiplied by 100. •The formula is (A/A+B) X 100. •From the previous slide: –The percentage of male deaths from AIDS was (0.83 X 100) = 83%. Rate Also a type of ratio, a rate differs from a proportion because the denominator involves a measure of time General Information Regarding Epidemiologic Measures provide the following types of information: ─frequency of a disease or condition ─associations between exposures and health outcomes ─strength of the relationship between an exposure and a health outcome Quantitative Epidemiologic Measures characterize the occurrence of disease, morbidity, and mortality in populations. Quantitative terms include: Counts, Incidence, Prevalence Count number of cases of a disease or other health phenomenon being studied. • single cases may have public health significance─Case reports of patients with particularly unusual presentations or combinations of symptoms often spur epidemiologic investigations. ─Ex one case of Ebola virus Incidence occurrence of new disease or mortality within a defined period of observation (time period) in a specified population. Population at Risk members of the population who are capable of developing the disease or condition being studied are known as the population at risk. Incidence Rate A rate formed by dividing the number of new cases that occur during a time period by the number of individuals in the population at risk Prevalence Number of existing cases of a disease or health condition, or deaths in a population at some designated time. •Variations: Point prevalence and Period prevalence/Lifetime prevalence Point Prevalence •All cases of a disease, health condition, or deaths that exist at a particular point in time relative to a specific population from which the cases are derived. •Formula: Point prevalence = Number of persons ill at a point in time Total number in the group Period Prevalence All cases of a disease within a period of time Lifetime Prevalence Cases diagnosed at any time during the person’s lifetime •Ex: Lifetime asthma diagnosis Interrelationships Between Incidence and Prevalence Factors that cause prevalence to increase: ─Increase in incidence ─Longer duration of the case ─In-migration of cases ─Prolongation of life of patients without a cure •Factors that cause prevalence to decrease: ─Decrease in incidence ─Shorter duration of disease ─In-migration of healthy people ─Improved cure rate of disease Crude Rate •A type of rate that has not been modified to take account of any of the factors such as the demographic make-up of the population that may affect the observed rate •Includes a time period during which an event occurred. •Numerator consists of the frequency of a disease over a specified period of time. •Denominator is a unit size of population.Aid in making comparisons but have limitations Crude Death Rate •The crude death rate is a type of crude rate. •Can be expressed in terms of any unit size of a population that is convenient. ─For example, infant mortality is expressed per 1,000 live births. Reference Population •The population from which cases of a disease have been taken •Ex: calculation of the annual crude death rate in the United States Case Fatality Rate (CFR) The number of deaths due to a disease that occur among persons who are afflicted with that disease= Number of deaths due to disease “X” Times 100during a time periodNumber of cases of disease “X” Proportional Mortality Ratio (PMR) The number of deaths within a population due to a specific disease or cause divided by the total number of deaths in the population Cause-Specific Rate A measure that refers to mortality (or frequency of a given disease) divided by the population size at the midpoint of a time period times a multiplier.Mortality (or frequency of a given disease) X 100,000Population size at midpoint of time period Age-Specific Rate (R) •The number of cases per age group of population during a specified time period Sex-Specific Rate The frequency of a disease in a gender group divided by the total number of persons within that gender group during a time period times a multiplier Adjusted Rate •A rate of morbidity or mortality in a population in which statistical procedures have been applied to permit fair comparisons across populations by removing the effect of differences in the composition of various populations •Age is a factor used in rate adjustment. AuthorAnonymous ID32869 Card SetEpidemiology chp 2 DescriptionEpidemiology chp 2 Updated2010-09-05T20:52:05Z Show Answers