Jill Sullivan 1

Pass in PsycInfo assignment 1

• review WWW assignment 2 due next week

• assign partners next week

• practice identifying independent/dependent variables

• practice identifying extraneous variables/ confounds

• Assignment 3 Variables

Jill Sullivan 2

IV/DV/Extraneous/Confound

Independent Variable: variables controlled by the experimenter in an attempt to test the effects on some outcome, the dependent variable

-variable that is manipulated by the experimenter. It is determined by the experimenter not the participant

Quasi-independent: existing quality, levels not assigned at random (ie. Age)

Dependent Variable: variable measured in a study. It is determined by the subject.

-The outcome variable of research

-dependent variable observed for effects due to the influence of another factor , the IV

Jill Sullivan 3

IV’s and DV’sIndependent Variable:

• the variable which is manipulated by the experimenter

• under the control of exp. (ie,. Independent of participants behaviour)

The set values or conditions of the IV are called the levels

ie. Interested in sleep deprivation and motor skills

• decide to have 3 levels:– 12 hours without sleep

– 24 hours

– 36 hours

Jill Sullivan 4

IV/ DV Example 1

ie. Interested in sleep deprivation and motor skills

• decide to have 3 levels:– 12 hours without sleep

– 24 hours

– 36 hours

Then you measure participants on a hand/eye coordination task

DV: score on coordination task

Jill Sullivan 5

Identify IV (levels) and DVExample 2

You’re interested in conducting a true experimental study to determine whether people are more satisfied after they succeed at an easy or a difficult task

IV: task difficulty

• # levels: 2; easy/hard

DV: satisfaction

Jill Sullivan 6

EXAMPLE 3 A Researcher conducts an experiment to determine the

effect of a new drug on the incidence of epileptic seizures. 40 epileptics are selected from the 150 epileptics being treated at a local hospital. 20 receive the new drug and 20 are given their traditional medication. The number of seizures in each of the participants is recorded for one month.

IV:

• type of medication

# Levels of IV?

• 2

• new drug, traditional drug

DV:

• number of seizures

Jill Sullivan 7

IV: manipulated by experimenterDV: what is measured and recorded

A Researcher conducts an experiment to determine the effect of a new drug on the incidence of epileptic seizures. 40 epileptics are selected from the 150 epileptics being treated at a local hospital. 20 receive the new drug and 20 are given their traditional medication. The number of seizures in each of the participants is recorded for one month

Jill Sullivan 8

Example 4

A researcher is interested in testing the effectiveness of type of reading program on children’s reading skills. Children are assigned to either a tutoring, tutoring and rewards, or no tutoring and no rewards group. Reading scores are recorded after two weeks time.

IV: type of reading program

• 3 Levels– tutoring

– tutoring and rewards

– no tutoring and no reward

DV: reading score

Jill Sullivan 9

IV/DV- Example 5

Would you take a drink of water from a fountain if someone were sitting right next to it? In an experiment investigating participants’ willingness to violate personal space, Barefoot, Hoople and McClay (1972) positioned a male or female experimenter near a water fountain. The experimenter was positioned either one foot (near condition), five feet (far condition) to the right of the fountain, or across from the fountain, ten feet away (control condition). The number of people passing the fountain was recorded along with how long a person spent at the fountain if he or she chose to drink. The results showed that fewer participants drank from the fountain in the near condition than in the far or control conditions.

IV: 1) distance the experimenter sat from the water fountain• levels (one foot, five feet, or 10 feet)

2) sex of experimenter 2 levels (male or female)

DV: 1) number of people who stopped to drink

2) amount of time spent at the fountain

Jill Sullivan 10

Extraneous Variables / ConfoundsUnjustified Conclusions

Extraneous Variables : any factors other than the independent or quasi-independent variables you’re considering that might affect scores on the dependent variable. (ie, age, noise)

Confounds; A confound or a confounding variable is an extraneous variable which varies systematically with your independent variable. It provides an alternative explanation for your results over and above your manipulation of the IV. (ie. A difference between conditions or groups other than what was intended).

Other problems; poor measurement of constructs, unjustified causal inferences

Jill Sullivan 11

Uncontrolled VariablesExample 1

An experimenter wanted to test the effects of music on learning by fourth grade children. To keep his work at a manageable level, he decided to introduce music into the classroom every afternoon for one week. No music would be played during the morning hours. The experimenter chose the music carefully, the music was from familiar tv cartoons, and the loudness was moderate. After the week of music presentation, the students were given tests on the morning and afternoon material. Test scores for the morning material were much higher than the scores on the afternoon material. Thus, the experimenter concluded that cartoon music disrupted learning in the classroom.

• Is the conclusion justified? Why or why not?

• No,

• Confound present : music played only in afternoon. Time of day may account for higher test scores

Jill Sullivan 12

Uncontrolled VariablesUnjustified Conclusions

More examples

Data: Fifty percent of women who take birth control pills have occasional hot flashes. Men almost never have hot flashes.

Conclusion: Birth control pills cause hot flashes

Conclusion justified?

No. Why not?

Correlation doesn’t prove causation. Hot flashes may occur in women even if they don’t take birth control pills.

Jill Sullivan 13

Uncontrolled Variables -Example 2

An experiment was designed to evaluate the effect of “subliminal perception” on thirst. The participants (university students) were randomly assigned to two groups. One group watched a movie (Return of the Pink Panther) that did not contain subliminal messages. The other group watched a movie (The Desert Fox) in which the message “Have a cool drink!” was repeatedly flashed on the screen so quickly that it was not consciously noticeable. Because of time limitations, the first group watched the movie at 8:30am, the second at 11:30am. The dependent measure was the amount of ice water consumed by the participants as they watched the movie. The second group drank significantly more ice water than the first; therefore, the researchers concluded that subliminal messages can affect thirst.

Jill Sullivan 14

Uncontrolled Variables -Example 2

Agree with their conclusion?

No. Why not? What’s the problem?

-2 confounds present:

time of day; people may be thirstier at 8:30 than 11:30

movie used: “Desert Fox” Has a dry connotation as opposed to “Pink Panther” , amount of water drank may be due to the movie not the subliminal message.

Jill Sullivan 15

Another Example

A researcher wants to examine the relation between personality and health habits. The researcher believes that people who have low self-esteem will be more likely to have unhealthy habits (e.g. smoking, overeating, poor dental hygiene). To conduct the research, the researcher distributes two questionnaires to all students currently enrolled in Introductory Psychology courses. The first questionnaire is a personality inventory that measures self-esteem. The second questionnaire is a survey of the person’s health habits. The researcher examines the data and concludes that self-esteem and unhealthy habits are related in this sample: those with lower self-esteem tend to engage in more risky personal health behaviours than those with higher self-esteem.

Jill Sullivan 16

• Any problems with this conclusion?

• Unjustified, why?

• Number of other factors left unexamined (extraneous variables) which could account for both low self-esteem and personal health behaviours– background

– income

– many plausible answers

• another extraneous variable: intro psyc students may differ in some manner than general population (external validity)

Jill Sullivan 17

Uncontrolled VariablesExample

An employee at a certain cafeteria wanted to show his boss that the policy of serving “exotic” juices with breakfast (if the customer requested it) was a wasteful practice. He thought people just bought the exotic juices to impress their friends and that they did not really like the taste of the juices. In order to gather evidence, the man recorded the flavour of the juice contained in the glasses of those patrons who failed to drink all of their juice. At the end of the morning he had counted a total of fifty less than completely finished glasses of juice. Of these, forty were of the exotic variety and only ten were of the non-exotic variety (orange juice). Because 80 % were of the unfinished juices were of the exotic variety, the employee concluded that his evidence was sure to convince his boss. Do you agree?

No…… Why not?

Unjustified conclusion; wrong adjustment made, need to adjust for #’s of each type of juice ordered, perhaps 200 people ordered exotic juices and 40 left unfinished, compared to 50 nonexotic and 10 left unfinished

Jill Sullivan 18

Practice!

Assignment 3- Variables assignment • Due in 2 weeks time• Oct 12 (A) Oct 14 (B/C)