Transcript Welcome Back - Bakersfield College

Welcome Back
Learning Objectives:
1.
Identify variables in research
2.
Describe Relationships btwn
3.
Explain why samples used to describe population
4.
Explain random sampling and representative
samples
5.
Distinguish btwn Descriptive & Inferential Stats
6.
Distinguish btwn experimental & correlational study
7.
Identify & distinguish scales of measurement
Research Process
Interest in something
– “Playing video games leads to violence”
– Goal: Discover LAWS OF NATURE
“Somethings” are called Variables
Variables
– Independent variables- the “thing” that
influences the behavior
– Dependent variables- the outcome or result
of the independent variable
Examples of Variables
Independent
–
–
–
–
–
Vegetables
Vitamins
Drugs
Smiling
Examples?
Dependent
–
–
–
–
–
Cancer
Immune System
Alzheimers
Helping or Altruism
Examples?
Relationship between Variables
Relationship: occurs when a chg in one var. is
accompanied by a consistent chg. in another
var.
Strength: Degree of chg in X is associated with
chg in Y
Types of relationships:
–
–
–
–
Increase, increase
Increase, decrease
Decrease, decrease
Zero
Populations & Samples
Population-all
members of group
Parameters-numbers
that describe
Every student at BC
Sample-subset of
pop designed to be
representative
Statistic-numbers that
describe
Students in a
History class
at BC
http://www.ruf.rice.edu/~lane/stat_sim/sam
pling_dist/
Why?
– Cheaper
– Practical
– Representative
What is “done” to samples?
Describe
– Use descriptive statistics to organize &
summarize characteristics of data
Example: The average test score was 87%
Infer
– Use inferential statistics to decide whether
sample data represents a particular
relationship in population
Example: Reading the textbook significantly
increased test scores.
Characteristics of a Study
Question about characteristic of sample or
pop is asked
Design study to answer question
– Who -How many
Conduct study
– Correlational
– Experimental
-When
-What
Correlational Study
Goal: To determine if relationship btwn two or
more var is present
No variables are manipulated or made to
occur, they are simply measured
As such cannot infer causality
– Can’t say X causes Y
– Only X and Y are related
Example
Researcher’s Question:
-Is there a relationship
btwn ice cream sales and
crime rate?
Design of study: measure
sales & crime rates
Yes, a positive, strong
relationship is present
– Doesn’t mean ice cream
causes crime
100
80
60
40
20
0
Ice Cream
Sales
Temperature
Experimental Study
Goal: To determine if relationship (causality) exists
btwn variables
Variable (indep) are manipulated or changed to see
chg in beh (dep var)
Can *infer causality
– X causes chg in Y
*Caution: causal statement based on probability
– Never says PROVES
– Other variables could be responsible for change in
dependent variable
Example
10
9
Number of Crimes
Committed
Researcher’s Question:
-Does ice cream cause or
have an effect on criminal
behavior
Design of study: P’s in diff
conditions of ice cream
(levels of indep var) and
measure criminal beh (dep
var)
Yes, a probable causal
relationship is present
– P’s that ate 1 or 2 scoops
of ice cream committed
more crimes
– PROBABILITY
8
7
6
5
4
3
2
1
0
0
1
Scoops of Ice
Cream
2
Type of Data or Characteristics of
Scores
Type of data or dependent var you’re
interested in will determine what statistic
you can use
– Numbers you record have diff mathematical
characteristics
Characteristics of numbers
– Levels of measurement
– Continuous or discrete
Scales of Measurement
Nominal Scale: scores used for
identification or naming. Ex: categories
Ordinal Scale: scores indicate rank or
ordering. Ex: relative amount
Interval Scale: scores indicate actual
amount. Ex: numbers
– **0 doesn’t necessarily mean non
Ratio Scale: scores indicate actual amount
Ex: numbers (0 actually means none)
Continuous or Discrete
Continuous: allows fractional amounts
(continues btwn whole numbers)
– Usually Scale (ratio & interval)
Test score 97.6
IQ score 145.9
Discrete: measures only whole numbers
– Usually Nominal or Ordinal
Male or Female
Eye color
– Can be Scale
Ice cream or no ice cream
No. of crimes 3
Let’s Graph
Questions?
Let’s get Active with a CLE
Homework: Finish Ch.1 & 2 study guid
– Review notes & text
– Finish Ch. 1 & 2 of study guide
– Preview Ch. 3
Bring
– Questions, book, calculator, pencils
Be ready for quiz