PsychStats (Prelims)

importance of statistics in psychology

• it is the backbone of psychological research and practice

• it transforms abstract themes into measurable insights and help Psychologists to make informed decisions

understanding human behavior

• statistics allows Psychologists to quantify thoughts, emotions, and behaviors

• they help identify patterns across individuals and groups, revealing trends that might otherwise go unnoticed

designing and Interpreting research

• psychological studies rely on statistical methods to test hypotheses

• tools like correlation, regression, and ANOVA help determine whether results are meaningful or due to chance

Evidence-Based practice

• therapies and interventions are validated through statistical analysis

• clinicians use data to choose treatment that are proven to be effective for specific conditions

critical thinking and objectivity

• encourages Psychologists to think critically and avoid biases

master the foundations

1st in how to gain the most in psychological statistics?

think critically about data

2nd in how to gain the most in psychological statistics

use the right tools

3rd in how to gain the most in psychological statistics

connect statistics to psychology

4th in how to gain the most in psychological statistics

stay curious and updated

5th in how to gain the most in psychological statistics

help each other

6th and last in how to gain the most in psychological statistics

psychology

it is the scientific study of the mind and behavior

describe, understand or explain, predict, control

Goals of psychology

statistics

• branch of mathematics that deals with the organization, summarization, analysis, and interpretation (OSAI)

• The science of collecting, analyzing, interpreting, and presenting data

• helps us make sense of the world by uncovering patterns, trends, and relationships within information

population

it is the entire group of individuals or entities that a researcher is interested in studying or making conclusions about

target population

the ideal group the researcher wants to understand

accessible population

the portion of the target population that the researcher can realistically reach

study population

the actual group selected for the study

why population matters?

• generalization

• validity

• sampling strategy

parameter

a value usually a numerical value that describes a population

Population Mean

it is the average score of a psychological trait, across all individuals in the population

Population Standard Deviation

how spread out those scores are

Population Proportion

it is the percentage of people in the population with a certain characteristics

why parameters matter

• foundation for inference

• benchmark for comparison

• used in models

sample

it is a subset of individuals selected from a larger population, used to make inferences about that populations psychological traits, behaviors, or conditions

representative sample

accurately reflects the characteristics of the population

random sampling

every individual has an equal chance of being selected to reduce bias

sample size

number of individuals in the sample

how samples are used

• estimate population parameter

• test hypotheses

• calculate confidence intervals

• run inferential statistics like t-test, ANOVA, regression

the relationship between a population and a sample

study a part to understand the whole

variables

it is the building blocks of research — they are the measurable traits, behaviors, or conditions that can change or vary across individuals, situations, or time

independent variable (IV)

it is manipulated by the researcher to observe its effect

dependent variable (DV)

it is the outcome measured to see if it changes due to the IV

extraneous variable

uncontrolled variables that might influence the DV

confounding variables

linked to both IV and DV, potentially distorting results

controlled variables

kept constant to prevent them from affecting the DV

intervening variables

psychological processes that mediate between IV and DV

value

the specific numbers or categories that a variable can take on

numerical values

numbers assigned to variables that represent measurable quantities

categorical values

labels or categories used to classify data

ordinal values

represents ranked data with a meaningful order but not equal intervals

binary values

only two possible outcomes

score

numerical value that represents a person’s performance, behavior, or response on a psychological test or assessment

raw score

unadjusted number of correct responses or points earned

standard score

transformed score that allows comparison across individuals or groups

z-score

indicates how far a score is from the mean in standard deviation unit

t-score

standardized score with a mean of 50 and SD of 10

percentile rank

shows the percentage of scores below a given range

scaled score

used in specific tests with fixed ranges

data (plural)

the information collected from observations, experiments, surveys, or assessments that helps Psychologists understand human behavior, thoughts, and emotion

quantitative

measurable and numeric

qualitative

descriptive and categorical

cross-sectional

collected at one point in time

longitudinal

collected over a period of time

experimental

from controlled studies

observational

from natural settings

data set

a structured collection of information gathered from participants in a study — used to analyze psychological traits, behaviors, or outcomes

descriptive statistics

tools researchers use to summarize, organize, and simplify data so they can understand patterns and communicate findings clearly

inferential statistics

tools that allow Psychologists to go beyond the data they have collected and make generalizations, predictions, or conclusions about a larger population

sampling error

the natural difference between the characteristics of a sample and those of the entire population it’s meant to represent

discrete variable

can take on specific, separate values. these values are countable and often whole numbers

continuous variable

can take any value within a given range

Dichotomous variable

also called as Binary variable, it has only two possible categories or values

artificial dichotomous

derived from the scores

True dichotomous

naturally occuring

Nominal scale

used to label variables that have no quantitative values

ordinal scale

used to label variables that have natural order, but no quantifiable difference between values

interval scale

used to label variables that have a natural order and a quantifiable difference between value, but no “true zero” value

ratio scale

used to label variables that have a natural order, a quantifiable difference between values and a “true zero” value

data structure 1

one group with one or more separate each

descriptive research

it involves measuring one or more separate variable for each individual with the intent of simply describing the individual variables

survey research

a useful way of obtaining data about people’s opinions, attitudes, preferences, and experiences that are hard to observe directly; data may be obtained using questionnaires and interviews

relationship between variables

two (or more) variables observed and measured; one of two possible data structures used to determine what type of relationship exists

data structure 2

one group with two variable measured for each individual

correlational method

two different variables are observed to determine whether there is a relationship between them

data structure 3

comparing two (or more) groups of scores

experimental method

in this research design, one (or more) variable is manipulated while another variable is observed or measured

independent variable (IV)

sometimes referred to as explanatory variable, is the variable that the experimenter intentionally manipulates

dependent variable (DV)

• sometimes referred to as outcome variable, it is the behavior being observed or measured by the experimenter

• the specific behavior that a researcher tries to explain in an experiment; the variable that is measured

experimental condition

a condition in an experiment wherein the subjects will receive the experimental treatment

control condition

a condition in an experiment wherein the subjects do not receive the experimental treatment

quasi experimental design

often seem like real experiments, but they lack one or more of its essential elements, such as manipulation of antecendents and random assignment to treatment conditions

pretest/post test design

a research design used to asses whether the occurrence of an event alters behavior; scores from measurements made before and after the event

nonequivalent groups design

a research design used to compare the effects of different treatment conditions on pre-existing groups of subjects; random assignment is not possible in this design

ex-post facto study

also known as casual-comparative design, is a study in which a researcher systematically examines the effects of pre-existing subject characteristics by forming groups based on theses naturally occurring differences between subjects

longitudinal design

a method in which the same group of subjects is followed and measured at different points in time; a mathod that looks for changes across time

descriptive statistics

procedure for summarizing a group of scores or otherwise making them more understandable

frequency distribution

an organized tabulation of the number of indicidual located in each category on the scale of measurement

frequency table

ordered listing of number individuals having each of the different values for a particular variable

portions

Measures the fraction of the total group that is aaociated with each score

percentage

an amount of something, often expressed as a number out of 100

Grouped frequency table

the number of individuals is given for each interval values

interval

range of values in a Grouped frequency table that are grouped together

histogram

barlike graph of a frequency distribution in which the value are plotted along the horizontal axis and the height of each bar is the frequency of the value; the bars are usually places next to each other without spaces, giving the appearance of a city skyline

frequency polygon

continuous line that represents the frequencies of scores within a class interval, based on a histogram; used for continuous data

column chart

used when comparing the frequencies of different categories with one answer

bar graph

identical to column chart, but in this chart, categories are organized vertically on the y-axis, and values are shown horizontally on the x-axis

line graph

used to show a trend in the data at equal intervals

pie graph

used when you want to show the proportion of an item that make up a series of data point