Statistics Quiz 1

statistics

branch of science that deals with DATA ANALYSIS and the study of it. The science of collecting, organizing and analyzing data for the purpose of estimation and making inferences.

population

all subjects possessing a common characteristic that is being studied

sample

A subgroup or subset of the population.

parameter

characteristic or measure obtained from a population

statistic

characteristic or measure obtained from a sample

descriptive statistics

collection, organization, summary, and presentation of DATA. Use GRAPHICAL DISPLAYS and NUMERIC summarizations to represent DATA.

inferential statistics

deals with procedures used to make inferences about a population parameter from information contained in a sample.

data

values which arise from observing from characteristics on a selected group of individuals. The characteristics which are observed are called VARIABLES.

variables

characteristic or attribute that can assume different values e.g. major, height, age, weight, gender.

qualitative

variables which assume non-numerical values. e.g. eye color, first name, favorite movie

quantitative

variables which assume numerical values. e.g. height, weight, income. DISCRETE or CONTINUOUS

discrete

variables which assume a finite or countable number of possible values. obtained by counting.

continuous

variables which assume infinite number of possible values. obtained by measurement. e.g. height of a person, amount of time spent studying. weight of an apple

levels of measurement

nominal, ordinal, interval, ratio

nominal

qualitative only. data values serve as labels, but labels have no meaningful order. e.g. hair color (blond, black, red, brown)

ordinal

qualitative or quantitative. Data values serve as labels but labels have natural meaningful order. Differences between values meaningless. e.g. class(fresh, sophomore, junior, senior)

interval

always quantitative. numerical data values so they have natural meaningful order, and differences are meaningful. ratios are meaningless.

ratio

always quantitative. numerical data values, have order, and both differences and ratios between values are meaningful.

sampling methods

random, systematic, stratified, cluster, convenience,

random sampling

data collected using chance methods or random numbers. same chance of being selected for the sample e.g. telephone polling, drawing names from a hat.

systematic sampling

data obtained by selecting ever kth object. e.g. choosing sample of voters by choosing every 25th voter from county voters roll. testing every 300th produce from assembly line.

stratified sampling

population is divided into groups (strata) according to some characteristic. Each strata is sampled using one of the other sampling techniques.

example of stratified sampling

choosing 200 men and 200 women for a sample, group population by income level & choose sample of low, middle, and high income individuals.

cluster sampling

population is divided into groups (geographically). Some groups are randomly selected, and all elements in those groups are selected. e.g. randomly choose 10 polling stations in a city and exit poll all voters at those stations

convenience sampling

choose individuals for a sample for easy to include. e.g. internet polls, mail-in customer survey.

observational study

observations and measurements of individuals conducted in a way that does not change the RESPONSE or the variable being measured.

experiment

TREATMENT is deliberately imposed on the EXPERIMENTAL UNITS in order to observe possible change in response or variable being measured. Common way to assign treatments to experimental units is by using random process.

treatment

level (amount) of factor applied to the experimental units

response

measured or observed traits in the experiment

experimental units

person, animal, plant, or thing, studied by a researcher

completely randomized design

one in which treatments randomly assigned to experimental units

CRD

treatments randomly assigned to experimental units

randomized complete block design

individuals first sorted into BLOCKS, & treatments randomly assigned to units in each block.

RCBD

individuals first sorted into BLOCKS, & treatments randomly assigned to units in each block.

data sources

secondary & primary

secondary data

data already available. Ex. statistical abstract of USA. Advantage: less expensive. Disadvantage: may not satisfy your needs.

primary data

data which must be collected

methods of collecting primary data

telephone interview, mail questionnaires, door-to-door survey, mall intercept, new product registration, personal interview, experiments