Epidemiology and Data

a collection of people who share common observable characteristics

population: all the people who live in a city, all people diagnosed with a disease (type 2 diabetes)

a measurable attribute of a population

parameter: average age of a population

a subgroup that has been selected, by using one of several methods, from the population

sample: want sample to be representative of the population

the degree to which characteristics of the sample correspond to the characteristics of the population from which the sample was chosen

representativeness

numbers that describe a sample

statistics

using sample-based data to make conclusions about the population from which the sample has been selected

estimation

methods for selecting a sample

- random: simple random sample, stratified random sampling

- nonrandom: convenience, systematic, cluster (these can lead to sampling bias)

Use of a random process to select a sample

simple random sampling

- choosing randomly from a list such as licensed drivers

a subgroup of the population (racial or ethnic group, age, socioeconomic status)

stratified random sampling: breaking populations into subgroups then choosing people from each subgroup

uses available groups selected by an arbitrary and easily performed method

convenience sampling: pulled records from drs office

uses a systematic procedure to select a sample of a fixed size from a sampling frame

systematic sampling

method of sampling in which the element selected is a group (as distinguished from an individual) called a cluster

cluster sampling: clearly defined, good for looking at SES

What are the types of data used in epidemiology?

- qualitative: employ categories that do not have numerical values (marital status, occupation, race/ethnicity)

- quantitative: data reported as numerical quantities (age, temperature, blood pressure)

data that have a finite or countable number of values (whole numbers)

discrete: children in a family, binary (two values) such as dead/alive or present/absent

data that have an infinite number of possible values along a continuum

continuous: height, weight, temp

What are stevens' measurement scales?

nominal, ordinal, interval, ratio

qualitative: ____________

- data which fall into mutually exclusive categories for which there is no natural order

nominal

ex: gender, religion, race/ethnicity, marital status

qualitative: ___________

- data which fall into mutually exclusive categories which have a rank order

ordinal

ex: grades, SES (poverty line), stage of disease

quantitative: ___________

- data which are measured by standard units

- the scale measures not only that one data point is different than another but by how much

- examples: the number of days since onset of illness, temperature in Fahrenheit or Celsius

interval

quantitative: ___________

- data which are measured in standard units where a true zero represents total absence of that unit

ratio

ex: number of children, temp in kelvin

the review of data for accuracy and completeness

data cleaning: identify outliers - values that differ greatly from other values in the data set

- data presented in tabular form such that each row of the table represents a case of the disease being investigated

- columns identifying info, clinical details, etc.

line listing

- visual display of the magnitude of the different categories of a single variable, with each category or value of the variable represented by a bar

simple bar graph

- histograms show epidemic curve

- used for data plotted against time

- can detect trends over long periods of time

line graph

shows components of a whole

pie chart

measure of ________ _________ (measure of location) - a number that signifies ___________ __________ of a group of numbers or of a distribution of numbers

central tendency, typical value

the number occurring most frequently

mode

middle point of a set of numbers, might use it if data is skewed

median

average

arithmetic mean

the difference between the highest and lowest value in a group of numbers

range

How to calculate midrange and how to calculate it for age

(minimum + maximum)/2

age: (minimum + maximum + 1)/2

degree of variability in a set of numbers

variance: reflects how different the numbers are from one another

measure of spread used most commonly with arithmetic mean

standard deviation

epidemiology

study of distribution and determinants of health-related states or events in a specific population and the application of this study to control health problems