w11 correlations

Question 1

alpha of .05 means….

Answer 1

there is 5% chance of rejecting a true null hypothesis

Question 2

Type 1 error means

Answer 2

false positive
rejected when should have retained null hypothesis

null was actually true

Question 3

Type 2 error means

Answer 3

false negative
Retained when should have rejected null

Question 4

degree of correlation =

Answer 4

• the extent to which there is a clear relationship between distributions of two variables
• measures the strength and direction of LINEAR relationships 2 variables

to which two or more variables are related

always about linear

Question 5

positive vs negative LINEAR correlation

Answer 5

Positive linear = high with high, both increase
negative linear = low with high, increase one decrease

Question 6

Scatterplot - line of best fit

Answer 6

high degree of correlation, points close to diagonal straight line

Question 7

Pearson’s r correlation steps

what does the ZxZy mean

Answer 7

1. you have the X and Y column values
2. find mean and SD
3. score-mean is (x-xbar), same for y
4. Zx = score-mean (the x-xbar value)/SD
5. ZxZy = multiply them
6. find pearsons r = add all the ZxZy/divide N
7. you have the correlation!
8. is it significant? t value (where n is number of data pairs)

COVARIANCE

Question 8

-1 <r< 1

Answer 8

size of r =0 no relationship
=0.4to0.6 moderate relationship
0.8 very strong
1 perfect relationship
- positive = direct relationship
- negative = inverse relationship

Question 9

what is r2(squared)

Answer 9

• rsquared is the shared variance
• coefficient of determination

Question 10

what affects the magnitude of a correlation?

Answer 10

influenced by
- outliers/extreme scores
- restricted range (range of responses)

if outlier smaller r
if restricted DV or IV, r also changes

Question 11

Pearson’s r HYPOTHESIS

Answer 11

Null = no relationship
alternative hypothesis = is relationship

Question 12

ZxZy =

sum of cross products

Answer 12

multiplied zx and zy scores for each participant
then add them up, divide by N to find ‘r’

Question 13

positive z score means
negative z score means

Answer 13

positive = above the mean
negative = below the mean

Question 14

Pearsons correlation assumptions

Answer 14

1. data is related pairs of values
2. interval or ratio scale
3. linear relationship
4. normality - normally distributed
5. no extreme outliers

Question 15

correlation is NOT causation because

Answer 15

there may be coincidence or other variables