Strengths and Weaknesses of Research Designs

Design Description Strengths Weaknesses

CorrelationalDesign

Researcher sees if changes in one variable are accompanied by systematic changes in another variable.

Researcher manipulates one of more independent variables to observe the effects on the dependent variable(s).

Experiment conducted in real-life, naturalistic settings.

Assignment of participants to groups is determined by their natural experiences

ExperimentalDesign

Quasi-experiment

Field Experiment

Useful when conditions do not permit the manipulation of variables.

Can isolate cause-and-effect relationships.

Can isolate cause-and-effect relationships; behaviors are observed in natural settings.

Takes advantage of natural separation of children into groups.

Cannot determine cause-and-effect relationships.

May not yield information about real-life behaviors.

Less control over treatment conditions.

Factors other than independent variables may be causing results.

In-depth observation of one or a few children over a period of time.

Single-CaseDesign

Do not require large pool of participants.

Ability to generalize to the larger population may be limited.

• Trust vs. Mistrust

• Autonomy vs. Shame and Doubt

• Initiative vs. Guilt

• Industry vs. Inferiority

• Identity vs. Role Confusion

• Intimacy v. Isolation

• Generativity vs. Stagnation

• Ego Integrity vs. Despair

ERIKSON’S PSYCHOSOCIAL STAGES

Birth – 1 year

1 - 3 years

3 - 6 years

6 - 12 years (Latency Period)

12 - 19 years (Adolescence)

19 – 25 years (Early Adulthood)

25 – 50 years (Adulthood)

50 years and older

PIAGET’S COGNITIVE STAGES

Sensorimotor

Preoperational

Concrete Operational

Formal Operational

Birth - 2 years

2 – 7 years

7 – 11 years

11 years - adulthood

Child develops schemes primarily through sense and motor activities

Child can think symbolically; holds egocentric view of the world

Child becomes able to manipulate logical relationships among concepts but only by generalizing from concrete experiences

Child is able to deal with abstractions, form hypotheses, solve problems systematically

The humanbody contains100 trillioncells.

There is anucleus insideeach humancell (except redblood cells).

Each nucleuscontains 46chromosomes,arranged in 23 pairs.

Onechromosomeof every pair isfrom eachparent.

Thechromosomesare filled withtightly coiledstrands ofDNA.

Genes are segmentsof DNA that containinstructions to makeproteins— thebuilding blocksof life.

Cell nucleus with a pair of chromosomes

Chromosomes split and replicate to producetwo identical pairs

The pairs separate, and the cell divides

Each daughter cell now has a pair of chromosomes that is identical to the original pair

The Process of Mitosis

The Germinal Stage of Prenatal Development

Zygote Implantation of the Embryo

Fallopian tube

Ovary

Uterus

Cervix

Vagina

Embryo joinedto uterine wall

Ovary

Blastocyst

Fallopian tube

Full termFetal period (in weeks)Embryonic period (in weeks)

3820 361612876543

Central nervous system

Heart

Period when majorabnormality occurs

Leg TeethArm

Eye

EyeHeart

Brain

Ear Palate Ear

External genitalia

Central nervous system

Heart

Arms

Eyes

Legs

Teeth

Palate

Period when minor defect orabnormality occurs

External genitalia

Ear

Spine

BladderPubic boneCervixVagina

Coccyx Rectum

Potential width of birth canal

The baby in the uterus before labor Water about to break (The baby's head now rests inside the cervix)

Transition: The baby in the birth canal

The baby about to be born The head rotates sideways after it emerges The delivery of the placenta

STAGE 1

STAGE 2 STAGE 3

InRev1The Apgar Scale

Score

0Characteristic

Heart rate

Efforts to breathe

Muscle tone

Skin color

Reflex irritability

Source: Apgar (1953)

1 2

Absent

Absent

Flaccid,limp

Body pale or blue

No response

Less than 100 beats per minute

Slow, irregular

Weak, inactive

Body pink,extremities blue

Frown, grimace

More that 100 beats per minute

Good; baby is crying

Strong, active motion

Body and extremities pink

Vigorous crying, coughing, sneezing

2 months(fetal)

5 months(fetal)

Newborn 2 years 6 years 12 years 25 years

Body Proportions, Fetal Period Through Adulthood

The Episode of the Strange Situation

Number of Episode Persons Present Duration Brief Description of Action

1

2

3

4

5

6

7

8

Mother, baby, and observer

Mother and baby

Stranger, mother, and baby

Stranger and baby

Mother and baby

Baby alone

Stranger and baby

Mother and baby

30 seconds

3 minutes

3 minutes

3 minutes or lessa

3 minutes or moreb

3 minutes or lessa

3 minutes or lessa

3 minutes

Observer introduces mother and baby to experimental room, then leaves.

Mother is non-participant while baby explores; if necessary, play is stimulated after 2 minutes.

Stranger enters. Minute 1: stranger silent. Minute 2: stranger converses with mother. Minute 3: stranger approaches baby. After 3 minutes mother leaves unobtrusively.

First separation episode. Stranger's behavior is geared to that of baby.

First reunion episode. Mother greets and comforts baby then tries to settle him again in play. Mother then leaves, saying bye-bye.

Second separation episode.

Continuation of second separation. Stranger enters and gears her behavior to that of baby.

Second reunion episode. Mother enters, greets baby, then picks him up. Meanwhile stranger leaves unobtrusively.

aEpisode is curtailed if the baby is unduly distressed.bEpisode is prolonged if more time is required for the baby to become involved in play.Source: Campos et al., 1983.