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# correlation - PowerPoint PPT Presentation

correlation. Are two variables related?. 1. Do they move together or opposite ?. 2. How strongly?. (if they are strongly related, we can predict one from the other). correlation coefficient. NO ASSN. NEGATIVE. POSITIVE. -1.00 0 +1.00.

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## PowerPoint Slideshow about ' correlation' - nell

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Presentation Transcript

Are two variables related?

1. Do they move together or opposite?

2. How strongly?

(if they are strongly related, we can predict one from the other)

NO ASSN

NEGATIVE

POSITIVE

-1.00 0 +1.00

= direction

+ / -

number

= strength

move together or opposite?

positive

correlation

+

negative

correlation

-

Variable 1

Variable 2

# of shoes you own

amt of credit card debt

move together, in same direction

POSITIVE

NEGATIVE

NO ASSN

To a group of people, give a questionnaire about their degree of shyness.

To this same group, give a questionnaire about their degree of happiness.

Each person has two scores. Use correlation.

Is there a relationship between shyness & happiness? (Did one cause the other?)

Correlation is NOT causation!

B

A

B

A

A

C

B

Variable 1

Variable 2

ice cream sales

violent crime

Ice cream sales positively correlate with the occurrence of violent crime.

e.g.

Variable 1

Variable 2

e.g.

NO ASSN

NEGATIVE

POSITIVE

-1.00 0 +1.00

= direction

+ / -

= strength

number

weak (0 - .40)

moderate (.41 - .69)

strong (.70 – 1.00)

NO ASSN

NEGATIVE

POSITIVE

-1.00 0 +1.00

= direction

+ / -

= strength

number

NO ASSN

NEGATIVE

POSITIVE

-1.00 0 +1.00

= direction

+ / -

= strength

number

Variable 1

Variable 2

+.90

height of twin #1

height of twin #2

+.50

marriage problems

behavioral problems in children

+.45

height of sister #1

height of sister #2

+.20

exposure to violent media

real-life violent behavior

-.40

amt of social support

frequency of illness

Hypothesis:

Systematic desensitization therapy eliminates phobias.

DEPENDENT VARIABLE

INDEPENDENT

VARIABLE