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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.