How we know
What we know
Research Fundamentals
Experimental Research | Descriptive Research |
variables manipulated & recorded | variables recorded |
variables in an around the expt. are controlled | variables in and around the study not controlled |
participants are (randomly) assigned to groups | participants not assigned to any groups |
variables include IV, DV, EV, confounds | variables include predictor & predicted |
stats used to detect differences between means | stats used to detect relationships among scores |
strength = cause & effect | strength = understanding relationships |
weakness = uncertain generalizability | weakness = confounds, no cause & effect |
Research Fundamentals
VARIABLES: What experiments are made of
Independent: the variable manipulated by the experimenter to see if the � manipulation affects some other variable.
“manipulated” means creating different groups or conditions
to be compared
Does teaching method affect _____? Create groups to compare online vs F-2-F
Does type of test affect ______? Create groups to compare open vs closed book
Does a teacher’s sex affect _____? Create groups to compare male vs female
Does vape juice flavor affect _____? Create groups to compare none, fruit, complex
Research Fundamentals
VARIABLES: What experiments are made of
Dependent: the variable affected by the IV…. that is, values of the DV will depend on which group or condition of the IV the participant was in.
Does teaching method affect test scores? See if test scores differ between online vs F-2-F�
Does type of test affect test anxiety? See if anxiety scores differ between open vs closed book�
Does a teacher’s sex affect student evals? See if eval scores differ between male vs female�
Does vape juice flavor affect daily puffs? See if # daily puffs differ b/w none, fruit, complex
Research Fundamentals
VARIABLES: What experiments are made of
Extraneous: any variable other than the IV or DV in an experiment
teaching method (test scores) | type of test (anxiety levels) | teacher’s sex (student eval) | vape juice flavor (# puffs per day) |
sex of teacher | sex of student | sex of student | sex of vaper |
sex of student | pre-existing anxiety levels | teaching method | vape device |
GPA | GPA | grade in class | vape cloud |
prof’s experience | testing location | teacher’s age | years vaping |
FR, SO, JR, SR | time of day | FR, SO, JR, SR | time of day |
Research Fundamentals
Confound: an extraneous variable that is systematically different between the groups, so that the experimenter no longer knows if it was the IV or the extraneous variable that produced the effect on the DV
teaching method |
sex of teacher |
sex of student |
GPA |
prof’s experience |
FR, SO, JR, SR |
teaching method
online | Face-2-Face |
male | female |
x x
x x
x x
mean mean
DV = test scores
Research Fundamentals
Confound: an extraneous variable that is systematically different between the groups, so that the experimenter no longer knows if it was the IV or the extraneous variable that produced the effect on the DV
type of test
open book | closed book |
low GPA | high GPA |
x x
x x
x x
mean mean
type of test |
sex of student |
pre-existing anxiety levels |
GPA |
testing location |
time of day |
DV= test anxiety
Research Fundamentals
Confound: an extraneous variable that is systematically different between the groups, so that the experimenter no longer knows if it was the IV or the extraneous variable that produced the effect on the DV
teacher sex
male | female |
C or lower | B or higher |
x x
x x
x x
mean mean
teacher’s sex |
sex of student |
teaching method |
grade in class |
teacher’s age |
FR, SO, JR, SR |
DV = student evals.
Research Fundamentals
Confound: an extraneous variable that is systematically different between the groups, so that the experimenter no longer knows if it was the IV or the extraneous variable that produced the effect on the DV
vape juice flavor
x x x
x x x
x x x
mean mean mean
vape juice flavor |
sex of vaper |
vape device |
vape cloud |
years vaping |
time of day |
none | fruit | complex |
small | medium | large |
DV = # puffs / day
Research Fundamentals
DESCRIPTIVE RESEARCH
Correlational Research
Two or more variables are observed, measured, and recorded to
see if they are related to each other.
The experimenter does not manipulate (create groups or conditions) for any of the variables.
He/she simply observes and records what’s already there.
Is the number of scars on the body related to age?
Is the number of years spent smoking related to years lived?
Are IQ scores related to annual income?
Research Fundamentals
DESCRIPTIVE RESEARCH
Correlational Research: STRENGTH
Typically, the data are analyzed with a statistic called the “correlation coefficient” “r”
-1 ---------------- 0 --------------- +1
Perfect No Perfect
Relationship Relationship Relationship
r = .77 r = .47 r = - .81
Research Fundamentals
DESCRIPTIVE RESEARCH
Correlational Research: DIRECTION
+r means as x increases, y increases OR
as x decreases, y decreases
-r means as x increases, y decreases OR
as x decreases, y increases
Is the number of scars on the body related to age?
Is the number of years spent smoking related to years lived?
Are IQ scores related to annual income?
r is positive
r is negative
r is positive
Correlation is NOT Causation
Even if the relationship the variables is perfect, this does not mean one “caused” the other!
X might cause Y
Y might cause X
a third variable might be the true cause
MEDIATING AND MODERATING VARIABLES
Mediator: a variable that explains why or how the IV had an effect on the DV
or why two or more variables are related (as in correlation)
Texting while driving increases driving errors
Why or how?
Texting is a distraction and distracted drivers make more errors
Distraction is the mediator
Moderator a variable that qualifies the effect of an IV on the DV in an � experiment by answering questions like “for whom”, “when”, or
“under what circumstances”. Moderators can also qualify the � relationship between variables as in correlation.
it is the “yes but” variable
Texting while driving increases driving errors
BUT
This is effect is greater for city driving than highway driving
Statistical Significance
Statistically Significant, p < .05 What does it mean?
The effect, difference, or relationship found is most likely a TRUE
effect, difference, or relationship
The probability that the effect, difference, or relationship is just
a chance finding is less than 5%
Just because a result is significant does NOT
mean it is important!