Statistics Test 1 vocab

discrete variable

obtained by counting, finite choices

qualitative data

measures of types and may be represented by a name, symbol or number code (categorical variables, ex: what type)

quantitative data

measures of values or counts and are expressed as numerical values (ex: how much, how often)

raw data

data that is not organized

relative frequency

proportion (or percent) or observations within a category found through the formula frequency/sum of all frequencies

frequency distribution

lists each category of data and the number of occurrences for each category of data

relative frequency distribution

lists each category of data together with the relative frequency

bar graph

constructed by labeling each category of data on either horizontal or vertical axis and the frequency/relative frequency on the other axis

Pareto chart

bar graph whose bars are drawn in decreasing order of frequency

pie chart

circle divided into sectors with each sector representing a category of data

continuous variables

obtained by measuring

nominal

only names

ordinal

names with an order, inconsistent intervals (Ex: first and second place)

interval

consistent intervals, no zero point

ratio

consistent intervals, starts at zero (zero means it doesn’t exist)

statistic

numerical summary of a sample

parameter

numerical summary of a population

descriptive statistics

organizing and summarizing data through summaries, tables, graphs

inferential statistics

uses methods that take a result from a sample, extend it to the population, and measure the reliability of the result

qualitative variables

classification based on characteristics

quantitative variables

numerical measures

observational study

measures characteristics of a population by studying a sample but does not attempt to influence the variables

designed experiment

applies a treatment to individuals and attempts to isolate the effect of the treatment on a response variable

lurking variable

variable that affects both variables of interest but is not acknowledged

confounding variable

explanatory variable considered in a study whose effect cannot be distinguished from a second explanatory variable (Ex: hot temperature affecting ice cream sales and sunburn severity)

cross-sectional study

collecting data about individuals at a certain point in time

case-control study

compares individuals with a particular characteristic with individuals who do not have that characteristic (the control), retrospective

cohort study

group observed over a longer period of time to determine if particular characteristics affect a response variable (most powerful)

confounding

the effects of 2+ explanatory variables are not separated

simple random sampling

sample of size n from population size N is obtained if every possible sample of size n have equal likelihoods of occuring

stratified sample

obtained by separating the population into non-overlapping groups (strata) and obtaining a proportional simple random sample from each group

systematic sample

obtained by selecting every kth individual from the population

cluster sample

obtained by selecting all individuals within a randomly selected collection or group of individuals

nonsampling error

error that results from an error in the survey process (undercoverage, nonresponse or response bias, data entry error)

sampling error

error that occurs from using a sample to estimate info of a population

sample without replacement

once an individual is chosen, it is removed from the population and cannot be chosen again

sample with replacement

selected individual is placed back into the population and could be chosen again

random sampling

using chance to select individuals for a sample from a population (should not be convenience based)

sampling bias

technique used to obtain the sample tends to favor one part of the population over another

undercoverage

proportion of one segment of the population is lower in a sample than is in the population (leads to sampling bias)

nonresponse bias

individuals selected to be in the sample who do not respond to the survey have different opinions from ones that do