Psych Midterm

Constructs

things that can’t be directly measured

Operational Definitions

identifies a measurement procedure for measuring a construct and uses those measurements to define the construct

Random Error

unpredictable fluctuations in data due to the uncontrollable factor

Systematic Error

consistent errors often due to poor methods and procedures

Reliably

how free data is from error

Validity

how free from systematic error

Population

all individuals of interest, described by parameters

Sample

set of individuals from the population to represent the population

Descriptive Statistics

summarizes and describes data, often with figures and graphs

Inferential Statistics

summarizes and interprets data with scores

Sampling error

the naturally occurring difference between a stat and the parameter

Discrete Variable

separate, indivisible categories

Continuous Variables

infinite number of possible values

Real Limits

bounds put on continuous variables

Nominal scale

discrete categories with no order implied

Ordinal Scale

discrete categories with order implied

Ratio Scale

has a meaningful zero

Interval Scale

arbitrary zero

Experimental Method

cause-effect relationship between two variables has manipulation and controls

Independant variables

the variable changed by reserachers

Dependant Variable

variable observed by researcher, often impacted by the IV

Confoudning Variable

external variables that influance the data

Random assortment

random formation of groups to avoid error

Matching

intentional forming of groups to avoid error

Correlational Method

two variables observed in same individuals, both continuous variables

Quasi Experimental

compares two variables, one discrete the other continuous, CAN NOT BE RANDOMLY ASSIGNED

Bar Graph

for nominal and ordinal data

Histograms

for interval and ratio data

Frequency Polyon

a line that shows frequency and trends

Population Graph

shows relative proportions

Central Tendancy

the center of distributions is and the single score that best represents the data

Skewed positive

tail to the right is longer >0

Skewed negative

tail to the left is longer <0

Varability

how spread out the data is

Mean

the avg of the data, needs the sum of scores and number of scores, adding new score changes it, adding a constant does not

Weighted Mean

the mean of two combined data sets

Median

The middle score of the set

Quartile

divides the data set into 4 parts (Q1, Q2, Q3, Q4)

Interpolation

the total interval distance

Mode

the most frequent scores

Major mode

the highest frequency scores

Minor Mode

the second highest frequent scores

Range

difference between the URL and LRL

Interquartile Range

distance between the 25th and 75th percentile

Semi Interquartile

half of the interquartile

Definitional Formulas

the “real“ forumla

Computational Formula

the short cut formula

Sample Stat Bias

when a sample stat systematically over or under estimates the population

z-score

how far a score is from the mean

Random sampling

every person has a chance to be picked, and the propability to be picked it equal

Law of Large numbers

the larger the sample, the closer the sample mean is to the pop mean

Central Limit Theorum

any population with a mean and SD will have a central tendancy the more sample means you collect. It will have a mean of mu, an SD of sigma/squareroot of n and will approach a normal curve as it approached infinity