STATS Unit 1 Review

statistics

the techniques for collecting, organizing, analyzing, and interpreting data.

raw data

a list of numbers or words that have been completely untouched.

data

pieces of information, such as numbers, words, measurements, observations, or descriptions of things in context.

data set

a single location which contains all of the information gathered on a topic presented in an organized fashion.

structured data

data that has easily identifiable structure such as rows and columns

variables

attributes measured in the course of a study

top row

displays the variables or attributes

other rows

data for a single record

variable of interest

attributes measured in a study

categorical (qualitative) variable

values that describe labels and attributes

nominal

categories with no distinct or defined order, or a difference in name only

nominal

ex: colors, names, gender, student ID

ordinal

variables that have an inherent or obvious order

ordinal

ex: olympic medals, class rank by GPA

numerical (quantitative) variables

have magnitude, are measureable, and units, with values that carry an equal weight

discrete

variables that can only take on specific values (typically integers)

discrete

ex: number of siblings, year of birht, IQ

continuous

variables that can take on any real number value

continuous

ex: height, temp., distance, dosage

population

collection of all possible members or outcomes for a group of interest

sample

a representative part or subset of a population

parameter

number that describes a population

statistic (experimental design)

number representing a sample

inference

process of estimating an unknown population value

simple random sample

sampling method where each member of the population has an equal chance of being selected

stratified random sample

a population is divided into smaller groups in which samples are taken

convenience sample

sample taken simply because it was easy to obtain

systematic sample

selecting every kth member

cluster sample

The population is divided into sections, sections are then randomly selected and every element is sampled

sampling error/variation

The natural variation from sample to sample which happens by chance.

bias

Systematic failure of a sampling method to represent a population.

Questionnaire/Interviewer Bias

A question is asked in such a way as to possibly alter the participants responses.

Instrument Bias

Can occur as a result of systematically measuring responses inaccurately, possibly due to a improperly calibrated scale.

Selection Bias

Individuals within a target population are more likely to be selected for inclusion than others.

Under- or Over-Representation

If the time and/or place a sample is taken makes it more or less likely for certain groups to be selected.

Nonresponse Bias

People selected to participate in a survey DO NOT complete it.

Voluntary Response Bias

Sample responses come from self-selected volunteers, results in non-representative samples

Confounding Variables

An external variable in a study affecting the relationship between study variables.

Lurking Variables

A variable that is unknown and not controlled for.

Possible Design Flaws

lurking and cofounding variables