Epidemiology Study Design
Epidemiological study in situations where nature is allowed to take its course. Changes or differences in one characteristic are studied in relation to changes or differences in others, without the intervention of the investigator.
What is observational study?
A rate limited to a particular age group. The numerator is the number of occurrences in that age group; the denominator is the number of persons in that age group in the population.
What is age specific rate?
A range of values for a variab le of interest, e.g., a rate, constructed so that this range has a specified probability of including the true value of the variable. The specified probability is called the confidence level, and the end points of the confidence interval are called the confidence limits.
What is a confidence interval?
A graphic representation of the freq uency distribution of a continuous variable. Rectangles are drawn in such a way that their bases lie on a linear scale representing different interval s, and their heights are proportional to the frequencies of the values within ea ch of the intervals.
What is a histogram?
The application of ______ in a population of interest to a standardized age distribution in order to eliminate differences in observed rates that result from age differences in population composition. This adjustment is usually done when comparing two or more populations at one point in time or one population at two or more points in time.
What is age adjustment?
A study in which the investigator specifies the exposure category for each individual (clinical trial) or community (community trial) then follows the individuals or community to detect the effects of the exposure.
What is an experimental study?
The numerator is the number of deaths attributed to a specific cause during a specified time interval; the denominator is the size of the population at the midpoint of the time interval.
What is cause specific mortality rate?
The central portion of a distribution, calculated as the difference between the third qu artile and the first quartile; this range includes about one-half of the observations in the set, leaving one-quarter of the observations on each side.
What is interquartile range?
A graphical technique for presenting discrete data organized so that each observation can fall into one and only one category of the variable. Frequencies are listed along one axis and ca tegories of the variable are listed along the other axis. The lengths of the bars represent frequencies of each group of observations.
What is a bar chart?
The first step in testing for statistical significance in which it is assumed that the exposure is not related to disease.
What is the null hypothesis?
A type of observational analytic study. Enrollment into the study is based on exposure characteristics or membership in a group. Disease, death, or other health-related outcomes are then ascertained and compared.
What is a cohort study?
The mortality rate from all causes of death for a population?
What is crude mortality rate?
A measure of association that quan tifies the relat ionship between an exposure and health outcome from a comp arative study; also known as the cross- product ratio.
What is an odds ratio?
A visual display that summarizes data using a box and whiskers format to show the minimum and maximum values (ends of the whiskers), interquartile range (length of the box), and median (line through the box).
What is a box plot?
An exposure, risk factor, or other characteristic being observed or measured that is hypothesized to influenc e an event or manifestation (the dependent variable).
What is an independent variable?
A type of observational analytic study. Enrollment into the study is based on presence (``case'') or absence (``control'') of disease. Characteristics such as previous exposure are then compared between cases and controls.
What is a case-control study?
A measure of the frequency with which an event, such as a new case of illness, occurs in a population over a period of time. The denominator is the population at risk; the numerator is the number of new cases occurring during a given time period.
What is incidence rate?
The set of numbers from 0 to 100 that divide a distribution into 100 parts of equal area, or divide a set of rank ed data into 100 class intervals with each interval containing 1/100 of the observations.
What is percentile?
A graph in which each dot represents paired values for two continuous variables, with the x-axis representing one variable and the y-axis representing the other; used to display th e relationship between the two variables; also called a scattergram.
What is a Scatter Diagram?
Deviation of results or inferences from the truth, or processes leading to such systematic deviation. Any trend in the collection, analysis, interpretation, publication, or review of data that can lead to conclu sions that are systematically different from the truth.
What is bias?
A type of experimental study with patients as subjects. The goal either is to evaluate a potential cure to prevent disease sequelae such as death or disability.
What is a clinical trial?
The proportion of persons in a population who have a particular disease or attribute at a specified point in time or over a specified period of time. do not differentiate between old and new cases of disease. It is a function of the incidence rate and the mean duration of illness.
What is prevalence rate?
The measure of central location commonly called the average. It is calculated by adding together all the individual values in a group of measurements and dividing by the number of values in th e group.
What is mean?
A graph of a frequency distribution with values of the variable on the x-axis and the number of observations on the y-axis; data points are plotted at the midpoints of the intervals and are connected with a straight line.
What is a frequency polygon?
This can occur when an association between a risk factor and disease can be explained by a factor associated with both disease and risk factor. For example, an association between smoking, alcohol consumption, and lung cancer is observed.
What is confounding?