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PSYC*1010 > PSYC*1010 Chapter 15: Correlation > Flashcards

PSYC*1010 Chapter 15: Correlation Flashcards

1
Q

What is correlation?

A

A statistical technique used to measure and describe the relationship between two variables

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2
Q

How many scores are required from each participant when computing correlation?

A

Two (one from each variable)

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3
Q

T or F: There is no attempt to manipulate or control variables in a correlation study.

A

True

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4
Q

What does the sign (+/-) of a correlation indicate?

A

The direction of the relationship

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5
Q

What is a positive correlation?

A

A correlation where two variables tend to change in the same direction

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6
Q

What is a negative correlation?

A

A correlation where two variables tend to change in opposite directions

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7
Q

T of F: The direction of a correlation is related to its strength.

A

False

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8
Q

What is the most common use of correlation?

A

To measure straight-line/linear relationships

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9
Q

What does the numerical value of a correlation indicate?

A

The strength/consistency of a correlational relationship

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10
Q

What is a perfect correlation?

A

A relationship where the actual data points perfectly fit the specific form being measured

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11
Q

What does a correlation of 1.00 indicate?

A

A perfect correlation

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12
Q

What does a correlation of 0 indicate?

A

No consistency between variables

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13
Q

What does the Pearson correlation measure?

A

The degree and direction of the liner relationship between two variables

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14
Q

What is the notation for the Pearson correlation of a sample?

A

r

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15
Q

What is the notation for the Pearson correlation of the population?

A

rho (ρ)

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16
Q

How is the Pearson correlation computed?

A

By dividing the covariability of X and Y by the variability of X and Y together

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17
Q

What is covariability?

A

The degree to which two variables vary together

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18
Q

What does the sum of products of deviations measure?

A

The degree of covariability between two variables

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19
Q

What notation is used to describe the sum of products of deviations

A

SP

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20
Q

When using a table to calculate SP and the Pearson correlation, what are the headings of each column?

A

X, Y, (X-M_X), (Y-M_Y), (X-M_X)^2, (Y-M_Y)^2, (X-M_X)(Y-M_Y)

21
Q

What happens when a constant value is added or subtracted from each X value?

A

The pattern of data points would shift to the right or left, but correlation stays the same

22
Q

What happens when a constant value is added or subtracted from each Y value?

A

The pattern of data points would shift up or down, but correlation stays the same

23
Q

What happens when each X or Y value is multiplied or divided by a constant positive?

A

Neither the pattern nor the correlation change

24
Q

What happens when each X or Y value is multiplied or divided by a constant negative?

A

A mirror image of the original pattern is produced and the sign of the correlation changes, but the numerical value doesn’t

25
Q

What is regression?

A

The process of using relationships to make predictions

26
Q

What is a common technique for demonstrating validity?

A

Correlation

27
Q

T or F: Correlations can’t be used to help measure and describe reliability.

A

False. They can.

28
Q

In terms of correlation, what indicates a good level of reliability?

A

A strong positive correlation

29
Q

In terms of correlation, what indicates poor reliability?

A

A weak correlation

30
Q

If a measurement procedure produces stable and constant measurements, what is it considered to be?

A

Reliable

31
Q

T or F: The prediction of a theory could be tested by determining the correlation between two variables.

A

True

32
Q

What are four considerations to bear in mind when encountering a correlation?

A
  • Correlation is not proof of a cause-and-effect relationship
  • The value of a correlation can be greatly affected by the range of scores in the data
  • One or two outliers can have a dramatic effect on the value of a correlation
  • Correlation shouldn’t be interpreted as a proportion
33
Q

What is the most common error in interpreting correlations?

A

Assuming that a correlation necessarily implies a cause-and-effect relationship

34
Q

What is needed to establish a cause-and-effect relationship?

A

A true experiment being conducted

35
Q

T or F: The correlation within a restricted range could be completely different from the correlation obtained from a full range.

A

True

36
Q

What is an outlier?

A

An individual with X and/or Y values that are substantially different from the values obtained for the other individuals in the data set

37
Q

What is the correlation of determination?

A

The effect size of a correlation

38
Q

What does the correlation of determination measure?

A

How much of the variance in one variable can be determined from its relationship with the other variable

39
Q

What is the notation for the correlation of determination?

A

r^2

40
Q

What does an r^2 value of 0.01 to 0.08 indicate?

A

A small effect

41
Q

What does an r^2 value of 0.09-0.24 indicate?

A

A medium effect

42
Q

What does an r^2 value of 0.25 or greater indicate?

A

A large effect size

43
Q

What does “regression toward the mean” refer to?

A

The fact that when there is a less-than-perfect correlation between two variables, extreme scores (high or low) for one variable tend to be paired with less extreme scores (closer to mean) on the second variable

44
Q

What are the null and alternate hypotheses for a two-tailed correlation test?

A

H0: ρ = 0 (no population correlation)
H1: ρ ≠ 0 (population correlation present)

45
Q

What are the null and alternate hypotheses for a one-tailed correlation test predicting a positive relationship?

A

H0: ρ ≤ 0 (population correlation not positive)
H1: ρ > 0 (population correlation positive)

46
Q

What are the null and alternate hypotheses for a one-tailed correlation test predicting a negative relationship?

A

H0: ρ ≥ 0 (population correlation not negative)
H1: ρ < 0 (population correlation negative)

47
Q

When a nonzero correlation is obtained from a sample, what are the two interpretations the hypothesis must decide between?

A
  • There is no correlation in the population and the sample value is the result of sampling error (H0)
  • The nonzero sample correlation accurately represents the nonzero correlation in the population (H1)
48
Q

How are degrees of freedom calculated for correlations?

A

df= n-2

PSYC*1010 (13 decks)

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