Chapter 1

Intro to Stats

Statistics \=

Statistics \= Basic Math + Context + Interpretation

Variables

Characteristics that can change or take on different values

Most research begins with a _

Most research begins with a general question about the relationship between 2 variables for a specific group

Population

An entire group of individuals

Label the 2 variables and population in the question: What’s the relationship between weekend drinking and academic performance among 1st year college students

weekend drinking is variable 1, academic performance is variable 2, 1st year college students is population

Sample

group of individuals selected to represent the population as usually populations are too large to examine the entire group

Inferential Statistics

Use sample data to make general conclusions about population

An example of inferential statistics

Presidential polling

Methods for organizing data

Tables or graphs

Methods for summarizing data

Descriptive values

Descriptive value for a population

parameter (the p’s go together)

Descriptive value for a sample

statistic (the s’s go together)

Sampling error

discrepancy between a sample statistic and its population parameter

Data

measurements obtained in research

Goal of statistics

to help researchers organize and interpret data

Discrete variables

consist of indivisible categories

Example of discrete variable

dice roll, score of football game, number of tickets sold

Continuous variable

categories that are infinitely divisible into any unit the researcher chooses

Example of continuous variable

time, weight, length

4 major scales of measurement

the scale chosen determines the types of questions that can be answered with the data: nominal, ordinal, interval, and ration

Nominal scale

an unordered set of categories identified by name only

Ordinal scale

an ordered set of categories, tells you the direction of difference between two individuals

Interval scale

an ordered series of equal sized categories, identify the direction and magnitude of a difference, zero point is located arbitrarily

Ratio scale

an interval scale where a value of zero indicates none of the variable, identify the direction and magnitude of differences

Which of the four levels of measurement categories and labels variables

Nominal, ordinal, interval, ratio

Which of the four levels of measurement ranks categories in order

Ordinal, interval, ratio

Which of the four levels of measurement has known equal intervals

Interval, ratio

Which of the four levels of measurement has a true or meaningful zero

Ratio

Goal of correlational studies

determine the strength and direction of the relationship between two variable

Correlational studies

uses observations of the two variables as they exist naturally

Correlation \________ causation

Correlation does not equal causation

Experiments

examine the relationship between 2 (or more) variables by changing one variable and observing the effects on the other variable

Independent Variable

a condition or event manipulated by experimenter (I decide)

Dependent Variable

an aspect of behavior thought to be affected by the independent variable (Depends on what I decide)

Nonexperimental studies

similar to experiments because they also compare groups of scores, do not use a manipulated variable to differentiate groups, the IV is a pre existing participant variable or a time variable

“X” or “Y” indicates

individual measurements or score obtained

“N” indicates

Number of individuals in a data set for a population

“n” indicates

Number of individuals in a data set for a sample

P in PEMDΣAS

calculations within parentheses are first

E in PEMDΣAS

exponents are second

MD in PEMDΣAS

multiplying and dividing are tied for third and must be completed from left to right

Σ in PEMDΣAS

Forth is summation with the Σ notation

AS in PEMDΣAS

Finally the remaining adding and subtracting is completed from left to right