PY 211 - Vocab Unit 1

statistics

mathematical procedures used to organize, summarizes, analyze, and interpret observations

data

numbers assigned to observations according to rules, called "scores" or "raw scores"

descriptive statistics

summarize, organize, describe score

inferential statistics

allows sample results to be generalized to representative populations

population

entire set of individuals or items of interest

parameter

data for a population

sample

representative subset of a population

statistics

data for a sample

variable

a characteristics that can have different values

examples for variable

stress level, age, gender, religion

value

a possible number or category that a score can have

examples for values

women, man,trans; 18-100;muslim,hindu,christian

score

a particular person's value on a variable

inventor of scales of measurements

S.S.Stevens (Harvard)

scales of measurement

degree to which measured variables conform to the abstract number system, determines the type of statistical analyses possible

types of scales of measurement

nominal, ordinal, interval, ratio

nominal (type of scales of measurement)

identity or classification (variable that has a name)

ordinal (type of scales of measurement)

rank or order

interval (type of scales of measurement)

order and equal units

ratio (type of scales of measurement)

order, equal units, and absolute zero

continous variable

diverse into an infinite number of fractional parts, possible decimals

discrete variable

separate and indivisible categories, whole numbers only

quantitative variable

varies by amount

qualitative variable

varies by form or class

frequency

describes the number of times or how often a category, score, or range of scores occurs

frequency distribution

a summary display for a distribution of data

ungrouped data

a set of scores or categories distributed individually, where the frequency for each individual score or category is counted

grouped data

set of scores distributed into intervals, where the frequency of each score can fall into any one interval

interval

discrete range of values within which the frequency of a subset of scores in contained

uses of frequency tables

describes the data, makes pattern of data clear, shows how many scores there are for each value on the scale

histogram

summarizes the frequency of continuous data that are grouped

unimodal frequency distribution

one peak

approximately bimodal frequency distribution

has 2 peaks

approximately rectangular frequency distribution

has a plateau

positively skewed distribution

tail goes toward the right

negatively skewed distribution

tail goes to the left

Leptokurtic distribution

sharper peak than normal, very thin

Platykurtic distribution

flat peak, more spread out

bar chart

summarizes the frequency of data in whole units or categories, nominal data

pie chart

summarizes the relative percent of discrete and categorical data into sectors

sector

represents the relative percentage of a particular category

scattergram

displays discrete data points to summarize the relationship between two variables, data points are plotted to see whether or not a pattern emerges

central tendency

most "typical" or common score

mode

most frequently occurring number in a distribution, used for nominal variables

median

value at which 1/2 of the ordered scores fall above and 1/2 fall below, middle score when all scores are arranged from lowest to highest

mean

sum of all the scores divided boy the number of scores (average)

measures of central tendency

in a normal distribution, mean, median,mode coincide

mean>median

in positively skewed distribution

mean

in negatively skewed distribution

variance

average of each score's squared difference from the mean
-negative is meaningless
-value can be 0 (no variability)

formula for variance

SD^2 = (X-M)^2 /N

formula for the standard deviation

square root of variance

standard deviation

the average distance of scores around the mean

68% (34% above mean, 34% below mean)

at least ... of all scores lie within one SD of the mean

95% (48% above mean, 48% below mean)

at least ... of all scores lie within two SD of the mean

99.7%

at least ... of all scores lie within three SD of the mean

z score

number of standard deviations a score is above or below the mean

formula to change a raw score to a z score

formula to change a z score to a raw score

property 1 of z score

sum of a set of z-scores is always 0

property 2 of z score

sd of a set of z-scores is always 1

normal curve table and z scores

shows the precise percentage of scores between the mean (z-score of 0) and any other z score

methods of sampling

random selection and haphazard selection

haphazard selection

Select items in a nonsystematic manner

probability

expected relative frequency of a particular outcome

outcome

result of an experiment