Chapter 1 quiz Flashcards
Nominal Scale
Categories are identified by name:
Gender: male, female
Political orientation: Republican, Democratic, Libertarian, Green
Categories represent qualitative differences
Ordinal Scale
A scale of measurement using ranks rather than actual numbers.(Birth order in family: first, second, third
Socioeconomic class: low, middle, high)
Interval Scale
An ordered series of equal-sized units.
We can determine the direction and size of a difference: how much higher, better, hotter.
It has an arbitrary zero.
It does not allow ratio comparison of measurements.
Ratio Scale
measurement that has a natural, or absolute, zero and therefore allows the comparison of absolute magnitudes of the numbers
What do psychologists use Statistics for?
Populations and Samples
Descriptive and Inferential Statistics
Variables
Scales of Measurement
Types of Studies
Statistical Notation
Population
The entire group of individuals we are interested in.(Do women smoke more than men? ex: Smokers)
Sample
Small group selected to represent the population.
Goal of Population and Sample
Numerical data used to measure and describe characteristics of groups. Includes measures of central tendency and measures of variation. (e.g., sample size, mean, standard deviation)
Parameter
Numerical summary of a population
Statistic
A numerical measurement describing some characteristic of a sample
N
Population size
n
Sample size
μ
Population mean
M
Sample mean
σ
Standard deviation of a population
SD
Standard deviation of a sample
Inferential Statistics
Procedures used to draw conclusions about larger populations from small samples of data
sampling error
an error that occurs when a sample somehow does not represent the target population
Variable
A factor that can change in an experiment ( ex: Does treatment X improve depression symptoms as compared with no treatment?
Treatment condition/ depression)
Construct
Internal characteristic that can not be directly observed
Discrete variables
Consist of separate, indivisible categories. No values can exist between two neighboring categories. (ex: Number of children a woman has = 2 or 3, not 2.6)
Continuous variables
Infinitely divisible into whatever units a researcher may choose
(Ex: Height = 64 inches or 64.4 inches or 64.3719 inches)
Scales of Measurement (Variables)
nominal, ordinal, interval, ratio
Experiments
to test the cause-effect relationship between two variables.
In an experiment one variable is manipulated, independent variable, and the other variable is measured, dependent variable.
Quasi-Experiments or Nonexperimental Studies
Ex: Effects of gender on verbal ability
-IV: gender
-Levels of IV: boys and girls
-DV: verbal scores.
A comparison is made b/w scores of two conditions of the IV. However,
No random assignment of participants to conditions occurs.
The effect may be the result of gender or something that varies with gender (e.g., verbal exposure).
Experiments in which pre-existing groups are used are quasi-experiments.
correlational study
A research project designed to discover the degree to which two variables are related to each other (Intelligence/academic performance: IQ tests, Academic tests)
Correlation does not mean causation
This shows the relation between two things, not how they were caused. You cannot determine causality, you can only determine correlation. For example, you can’t say less sleep causes more stress or vice versa.
Correlation
The relation of the variables is measured using a statistic
X
Score on a 5-point quiz, If there is only one variable, the scores for that variable are represented by this…..
Y
If there is a second variable, the scores for that variable are represented by this…..
Σ
“the sum of”
ΣX
Sum of the X scores
Σ (X-1)
Parentheses indicate that you should perform the operation in parentheses before you do the summation
Example of Statistical Notation
X: quiz scores
X: 3, 3, 5, 2, 5, 4
ΣX: 3+3+5+2+5+4
ΣX= 22
Σ (X-1)= (3-1)+ (3-1)+ (5-1)+ (2-1) + (5-1) + (4-1)
Σ (X-1)= 2+ 2+ 4+1+4+3
Σ (X-1)= 16
Order of Operations
the order in which operations in an expression to be evaluated are carried out.
1. parentheses
2. exponents
3. multiplication and division
4. addition and subtraction
