Population
a collection of all outcomes responses measurements or counts that are of interest
Sample
part of a population
Parameter
numerical description of a population characteristic
statistic
a numerical description of a sample characteristic
Descriptive statistics
the branch of statistics that involves the organization summarization and display of data
Inferential Statistics
the branch of statistics that involves using a sample to draw conclusions about a population. A basic tool in the study of inferential statistics is probability
Qualitative data
consists of attributes, labels, or nonnumerical entries
Quantitative data
consists of numerical measurements or counts
Nominal level of measurement
qualitative only. stat at this level are categorized using names, labels or qualities. No mathematical computations
Ordinal level of measurement
qualitative or quantitative. can be arranged in order, or ranked, but differences between data entries are not meaningful
interval level of measurement
can be ordered an meaningful differences between data entries can be calculated. At the interval level a zero entry simply represents a position on a scale. the entry is not an inherent zero (eg temperature)
ratio level of measurement
similar to data at the interval level with added property that a zero entry is an inherent zero. a ratio of two data values can be formed so that one data value can be meaningfully expressed as a multiple of another
Observational study
researcher observes and measures characteristics of interest of part of a population but does not change existing conditions
Experiment
a treatment is applies to part of a population and responses are observed. Another part of the population may be used as a control group as well as parts that are given a placebo
Simulation
the use of a mathematical or physical model to reproduce the conditions of a situation or process
Survey
an investigation of one or more characteristics of a population. most often carries out on people by asking them questions
confounding variable
occurs when an experimenter cannot tell the difference between the effects of different factors on a variable
Blinding
a technique where the subjects do no know whether they are reciving a treatment or a placebo.
Double-Blind experiment
neither the experimenter nor the subjects know if the subjects are receiving treatment or a placebo
Randomization
is a process of randomly assigning subjects to different treatment groups
Replication
is the repetition of an experiment under the same or similar conditions
Census
count or measure of an entire population
sample
part of a population
random sample
one in which every member of the population has an equal change of being selected
simple random sample
a sample in which every possible sample of the same size has the same chance of being selected
Stratified sample
when it is important for the sample to have members from each segment of the population
cluster sample
when the population falls into naturally occurring subgroups, each having similar characteristics
Systematic sample
a sample in which each member of the population is assigned a number. The members of the population are ordered in some way, a starting number is randomly selected and the sample members are selected at regular intervals from the starting point
convenience sample
consists only of available members of the population. usually bias