Nature of Nature of ResearchResearch

Pt 2Pt 2

Definitions:Definitions:

CONSTRUCT:

• a fabrication of mind, invisible, unmeasurable.

THEORY:

• built of constructs,

• showing relationships between constructs,

• a systematic view of phenomena to explain and/or predict,

THEORY:

• a network of related constructs,

• abstract.

Theory consists of:

1. Definitions, explication of constructs.

2. Operational Definitions.

Theory consists of:

• what we wish to measure, observe or manipulate.

Theory consists of:

• criteria: must exhaust the definition of the constructs, must be exclusive (not include additional things).

Theory consists of:

•Explication of constructs. •Operational Definitions. •What we wish to measure, observe or manipulate. •Criteria

VARIABLE: Any quality that has

more than one value.

HYPOTHESIS: Pertaining to the expected relationships among variables.

• Must be specific expression of expected answer about relationships among variables.

• Interaction of operational definitions, concrete, observable.

HYPOTHESIS

From testing of the hypothesis one draws inferences which may allow generalization based on the theory.

HYPOTHESIS

VARIABLES

• can be added to sharpen the prediction, provide more explanation.

VARIABLES

Independent Variable: cause.

Dependent Variable: effect.(depends on independent variable)

“If [I.V.] then [D.V.].”

VARIABLES

Moderator Variable: moderates the effect

of I.V. on the D.V.

More than one variable effects outcome.

VARIABLES

Mediated Variable: one that intervenes, allows

one variable to act upon another.

VALIDITY: Internal• experiment is well

controlled, clean.• clearly measures what

is concluded.• clearly tests the

question asked, the target question.

• with no confounding variables

VALIDITY: External

• artificiality of created situation.

• is the conclusion generalizable outside of experimental situation?

VALIDITY: External

Ex. Piaget studied his own children.Can this be generalizable?

A problem of Sample Validity.

VALIDITY: External

Ex. Study of violent tv watching.Experimental Groupwatches 3 hrs. of violent tv.

VALIDITY: External

Ex. Study of violent tv watching.Experimental Groupwatches 3 hrs. of violent tv.No Control Group.No Choices given.

A problem of Extreme Treatment.

Measurement

Is behavior observed a typical expression of what is to bemeasured?

Ex. What does “time-on-task” measure?

CAUSAL RELATIONSHIP

• must show statistical relationship

• must precede event

• must rule out plausible rival hypotheses

(PRH)

CONTROL GROUP

• Ask, What is it designed to control for?

• Must be equivalent to experimental group.• Function: to rule out Plausible Rival

Hypothesis.

Threats to Internal Validity

• HistoryIf the study has multiple

phases, there may be an influence by the early

phase on the later phases.

Threats to Internal Validity

• TestingAll participants must be sensitized to the same

extent.

Threats to Internal Validity

• MortalityIf dropouts are not

equally distributed (randomly) there may be systematic bias.

Threats to Internal Validity

• MaturationParticipants would

improve anyway by growing up.

HAWTHORNE EFFECT:

Effect of attention paid to participants.

Threats to Internal Validity are less important in correlational studies than in functional studies. (A correlational study does not show causal relationship.)

Regression Toward the Mean

Performance varies, and over time values will

gravitate to the mean.

Highs become lower, and lows become higher.

Random Assignment

(Random Selection)Allows for comparability between

experimental group and control group.Each individual has the same chance to

be in either group.Otherwise there may be bias.

(RA)(RS)

Sampling

Science of choosing representationally fromeach ethnic, racial, age, class, etc., group.Allows validity with only1100 polled of 260 million.

Precision

Difference between groups_______________________

Difference between individualswithin group

=

Precision

D B_____

D W

= Probability (p)

Standard Deviation

Size of variability of distributionof individual differences.

Mean (x) yields some information,not necessarily meaningful.Range tells more of the story.

Standard Deviation

Shoe Sizes Mean (x)

8 8.5 10 9.5 9.0

11.5 6 12 6.5 9.0

A

B

Standard Deviation Shoe size Mean Deviation SS Variation Std Dev

(x) (s2) (σ)

11.5 9 2.5 6.25 1.566 9 -3 9 2.2512 9 3 9 2.256.5 9 -2.5 6.25 1.56

2.76 (x)2 /SSN

Standard Deviation

6 7 8 9 10 11 12

X

Standard Deviation

6 7 8 9 10 11 12

X

Standard Deviation

6 7 8 9 10 11 12

X

Standard Deviation

6 7 8 9 10 11 12

X

Standard Deviation

6 7 8 9 10 11 12

X

Statistical Significance

“Significance of difference” or, meaningfulness.

Statistical Significance

Ex. Grp #1–Individual InstructionGrp #2–Group Instructionn=30 in each group(could be 3000)RA, RS

Grp. #1 does 3 pts. better on posttest.Is that Significant?

Statistical Significance

Ex. Grp #1–Individual InstructionGrp #2–Group Instructionn=30 in each group(could be 3000)RA, RS

Grp. #1 does 3 pts. better on posttest.Is that Significant?

What is the probability that observed differences between the Experimentalgroup and the Control group is due tochance?

Probability (p)

p = (probability that difference is due to chance)[+ –] .0595% sure of significance

N.B.Level of significance is not levelof importance.

Probability (p)

p = >.05 is the agreed upon standard >.07 is acceptable

End part 2