Data
consist of information coming from observations, counts, measurements, or responses
statistics
the science of collecting, organizing, analyzing, and interpreting data in order to make decisions
population
the collection of all outcomes, responses, measurements, or counts that are of interest
sample
subset of a population
parameter
a numerical description of a population characteristic
statistic
numerical description of a sample characteristic
Descriptive statistics
the branch of statistics that involves the organization, summarization, and the display of data
inferential statistics
the branch of statistics that involves using a sample to draw conclusions about a population. As base tool in the study of inferential statistics is probability
Qualitative data
consists of attributes, labels, or nonnumerical values
Quantitative data
consist of numerical measurements or counts
Nominal level of measurement
qualitative only. Data at this level are categorized using names, labels, or qualities. No mathematical compuataions can be made at this level
Ordinal level of measurement
qualitative or quantitative. Data at this level can be arranged in order, or ranked, but differences between data entries are not meaningful
interval level of measurement
can be ordered, and you can calculate meaningful differences between data entries. At the interval level, a zero entry simply represents a position on a scale; the entry is not an inherent zero
Ratio level of measurement
are similar to data at the interval level, with the 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
researecher observes an measures characteristics of interest of part of a population but does not change existing conditions
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
confounding variable
occurs when an experimenter cannot tell the difference between the effects of different factors on a variable
placebo effect
occurs when a subject reacts favorably to a placebo when in fact, he or she has been given no medicated treatment at all
blinding
a technique where the subject does not know wheter he or she is receiving a treatment or a placebo
double-blinds experiment
neither the subject nor the experimenter knows if the subject is receiving a treatment or a placebo.
Randomization
is a process of randomly assigning subjects to different treatment groups
blocks
groups of subjects with similar characteristics
randomized block design
divide subjects with similar characteristics into blocks, and then within each block, randomly assign subjects to treatment groups
Matched-pairs design
where subjects are paired up according to a similarity
replication
the repetition of an experiment using a large group of subjects
census
a count or measure of an entire population
sampling
count or measure of a part of a population
sampling error
the difference between the results of a sample and those of the population
random sample
is one in which every member of the population has an equal chance of being selected
simple random sample
sample in which every possible sample of the same size has the same chance of being selected
Stratified Sample
when you want members from each segment of the populatoin. Members of the population are divided into two or more subsets that share a similar characteristic
Cluster Sample
when the population falls into naturally occuring subgroups, each having similar characteristics. Divide the population into groups, and select all of the members in one or more (but not all) of the clusters.
Systematic Sample
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 then sample members are selected at regular intervals from the starting number
Convenience sample
consists only of available members of the population
Frequency Distribution
is a table that shows classes or intervals of data entries with a count of the number of criteria in each class. The frequency f of a class is the number of data entries in the class
Class limit
the lower class limit is the least number that can belong to the class and upper is the biggest
Class Width
the distance between lower (or upper) limis of consecutive classes.
Midpoint
the sum of the lower and upper limits of the class divided by two. Also known as the class mark
Relative Frequency
the portion or percentage of the data that falls in that class.
Cumulative Frequency
the sum of the frequency for that class and all previous classes
Frequency Histogram
bar graph that represents the frequency distribution of a data set
Class Boundaries
the numbers that separate classes without forming gaps between them
Frequency Polygon
line graph that emphasizes the continuous change in frequencies
Cummulative Frequency Graph or OGIVE
a line graph that displays the cumulative frequency of each clas at its upper classs boundary.