Unit 3

Question 1

what is correlation

Answer 1

describes the relationship between two variables

Question 2

what is a scatterplot or scatter diagram

Answer 2

shows the pattern of correlation between two variables
a graph that shows hte degree of direciton of relationship between two variables

Question 3

what are the two variables in a scatter plot and what axis are they located on

Answer 3

predictor/causing variable - x axis
criterion variable - y axis

Question 4

what are the three patterns of correlation for a scatter diagram

Answer 4

positive
negative
no correlation

Question 5

in a positive correlation what happens with the variables

Answer 5

both increase together

Question 6

what happens with the two variables in a negative correlation

Answer 6

the criterion variable decreases as the predictor variable increases

Question 7

what can be said about the variables in a no correlation scatterplot

Answer 7

that they are independent of one another

Question 8

what are the two shapes for the trend line or line of best fit

Answer 8

linear or curvilinear

Question 9

what is the indpendent variable

Answer 9

the variable that is presumed to cause change in the dependent variable
difference between the control and experimental group
changed to test a hypotheis

Question 10

what is the dependent variable

Answer 10

the thing being measured

Question 11

what axis do the independent and dependent variable go on

Answer 11

indpendent -x
dependent - y

Question 12

what is the formula for a regression line

Answer 12

Y = mx + b

Question 13

what do the values in Y=mx+b represent

Answer 13

y is the depdendent variable
m is the slope of the line
b is where the line intersects the x axis where y is 0

Question 14

what is the name of the value that tells us the strength and direction of a linear correlation

Answer 14

pearson correlation coefficient (r)

Question 15

what does the Pearson correlation coefficient tell us

Answer 15

the strength and direction of a linear correlation

Question 16

if data points are far away from the regression line what does this mean

Answer 16

it is a weak correlation

Question 17

if data points are close to the regression line what does this mean

Answer 17

that it is a strong correlation

Question 18

what type of statistic is the pearson correlation coefficient

Answer 18

descriptive statistic

Question 19

what is the range of values for the correlation coefficient r

Answer 19

-1.00 and +1.00

Question 20

what is the cross product of z scores from your two data sets

Answer 20

correlation coefficient (r)

Question 21

what r values indicate a weak correlation

Answer 21

0-0.29

Question 22

what values for the correlation coefficient indicate a moderate correlation

Answer 22

0.3-0.5

Question 23

what r values indicate a strong correlation

Answer 23

> 0.5

Question 24

what are the 5 steps in calculating the Pearson correlation coefficient (r)

Answer 24

1. calculate the mean and standard deviation for each variable
2. change all raw scores to Z scores
3. caclulate the cross product of the Z scores for each person
4. sum the cross products of Z scores
   divide by the number of people in the study

Question 25

what value tells us the amount of variation accounted for by the indpendent variable

Answer 25

coefficient of determination

Question 26

what is the difference between r and r²

Answer 26

r = how strong and in what direction the relationship is. r² = how much of the variation in one variable is explained by the other.

Question 27

explain the issues of causality when interpreting a correlation coefficient

Answer 27

correlation does not prove causation x could cause y y could cause x another third factor could be causing both x and y

Question 28

how would you predict the Z score of the dependent or critierion variable

Answer 28

Predicted Zy = (β)(Zx)

Question 29

what is β

Answer 29

The standardized regression coefficient

Question 30

what is another name for the dependent variable

Answer 30

criterion variable

Question 31

what is another name for the independent variable

Answer 31

predictor variable

Question 32

what does the coefficient of determination r^2 tell us?

Answer 32

the amount of variation accounted for by the independent variable

Question 33

why do we need both r and r^2

Answer 33

r tells us the strength and direction r^2 indicates the amount of variation accounted for by X

Question 34

is r or R^2 used for ANOVA testing

Answer 34

R^2 - used for multiple correlations or multiple regressions

Question 35

what r value would indicate a perfect correlation

Answer 35

-1.00 or + 1.00

Question 36

what is the correlation coefficient

Answer 36

represented by r a statistical index of the relationship between two things -1 to +1

Question 37

what is a true experiment

Answer 37

the only research strategy that can determine that something causes something else

Question 38

what is the direction of causality

Answer 38

path of casual effect; if X is thought to cause Y then the direciton of causality is from X to Y

Question 39

what is a longitudinal study

Answer 39

research in which the same people are restuided and retested over a long period

Question 40

What does the standardized regression coefficient β represent

Answer 40

regression coefficient in a prediction model using Z scores

Question 41

what is a correlation matrix

Answer 41

common way of reporting correlation coefficients amonth several variables in a research article

Question 42

what is multiple correlation

Answer 42

a correlation between one variable and a combined set of predictor variables

Question 42

what is multiple regression

Answer 42

procedure for predicting scores on a criterion variable from scores on two or more predictor variabels

Question 43

What do the asterisks mean in a correlation matrix

Answer 43

statistical significance - associated p values are at the bottom of the matrix

Question 44

what is multiple correlation

Answer 44

association between criterion variable and two or more predictor variables

Question 45

what is a multiple regression

Answer 45

procedure for predicting scores on a criterion variable from scores on two or more predictor variables

Question 46

a correlation descibes the relationship between two ________________

Answer 46

equal-interval numeric variables

Question 47

what are two ways researchers can rule out alternative directions of causality

Answer 47

longitudinal study conduct a true experiment

Question 48

the corrrelation coefficient is also called the

Answer 48

proportion of variance accounted for

Question 49

what is the association of a criterion variable with two or more predictor variables

Answer 49

multiple correlation

Question 50

if the correlation coefficient is .6 what is the proportion of variance accounted for?

Answer 50

.36

Question 51

does a correlation coefficient of 0 necessarily mean that two variables are not correlated?

Answer 51

not necessarily - it doesn't mean there is no relationship. only that there is no linear relationship

Question 52

What are 5 ways in which the correlation coefficient improves our understanding of a relationship beyond what is shown in the scatter diagram

Answer 52

1. quantifies strength of the relationship 2. measures the direction 3. gives a standardized measure 4. detects linear relationships 5. allows for statistical testing

Question 53

Why are Z scores used to calculate a linear regression btw two variables (3)

Answer 53

1. standardize the variables 2. simplify regression math 3. make the slope equal to the correlation

Question 54

what do r² and R² tell us

Answer 54

r²: (only one predictor) the proportion of variance in Y that is explained by X R²- (two or more predictors) the proportion of variance in Y explained by all predictors combined

Question 55

what would you say about an r=0.87

Answer 55

statistically significant and that there is low likelihood that the findings occurred by chance

Question 56

What would you say about r=0.15

Answer 56

not statistically significant and that you cannot conclude that there is a relationship between the variables

Question 57

When would you caclulate r²

Answer 57

when there is a strong correlation between variables which tells us the proportion of varaiation in the criterion variable that can be explained by the predictor variable

Question 58

what type of data is hte mean the best? median? mode?

Answer 58

mean - symmetrical distributions median - skewed distirbutions mode - nominal data

Question 59

define variance

Answer 59

average squared deviation from the mean

Question 60

difference between measures of central tendency and representative values

Answer 60

central tendency - statistics that affect the center of a distribution, mean, median and mode CENTER OF DATA representative values - any statistic that represents the data set as a whole mean, median, mode, standard deviation, variance and range center + spread + standardized values