Exam 2 - Statistics

Question 1

what measures the outcome of a study

Answer 1

response variable

Question 2

what explains or causes changes in the response variables

Answer 2

explanatory variable

Question 3

what kind of plot shows the relationship between two quantitative variables measured on the same individuals

Answer 3

scatterplot

Question 4

when above-average values of one tend to accompany above-average values of the other and below-average values also tend to occur together

Answer 4

positive association

Question 5

when above-average values of one tend to accompany below-average values of the other, and vice versa

Answer 5

negative

Question 6

the direction and strength of the linear relationship between two quantitative variables

Answer 6

correlation

Question 7

the magnitude of r

Answer 7

strength

Question 8

if the correlation is zero, then the slop of the least-squares regression line is

Answer 8

zero

Question 9

b1

Answer 9

slope

Question 10

b0

Answer 10

intercept

Question 11

what is the straight line formula

Answer 11

y(hat) = b0+b1x

Question 12

a straight line where we have data on an explanatory variable and a response variable

Answer 12

least-squares regression line

Question 13

slope’s equation

Answer 13

b1=rSy/Sx

Question 14

intercept equation

Answer 14

b0=y-b1x

Question 15

square of the correlation

Answer 15

r^2

Question 16

the fraction of the variation in the values of y that is explained by the least-squares regression of y on x

Answer 16

r^2

Question 17

the use of a regression line for prediction far outside the range of values of the explanatory variable x used to obtain the line

Answer 17

extrapolation

Question 18

the difference between an observed value of the response variable and the value predicted by the regression line

Answer 18

residuals

Question 19

if the regression line is a good fit for the data, then

Answer 19

no obvious pattern should be shown in the residual plot

Question 20

an observation that lies outside the overall pattern of other observations

Answer 20

outliers

Question 21

points that are outliers in the y direction of a scatterplot have…

Answer 21

large regression residuals

Question 22

If removing an observation for a statistical calculation markedly changes the result of the calculation then it is

Answer 22

influential

Question 23

an association or comparison that holds for all of several groups can reverse direction when the data are combined to form a single group

Answer 23

simpson’s paradox

Question 24

when two variables effects on a response variable cannot be distinguished from each other

Answer 24

confounding

Question 25

confounded variables can be either

Answer 25

explanatory variable or lurking variable

Question 26

the observed association between the variable x and y is explained by a lurking variable z

Answer 26

common response

Question 27

the strength of the association influences the …?

Answer 27

precision of determining the value of the other variable

Question 28

correlation makes no distinction between

Answer 28

explanatory and response variables

Question 29

r has no

Answer 29

units

Question 30

correlation requires that both variables be

Answer 30

quantitative

Question 31

error =

Answer 31

y-b0-b1x

Question 32

so error =

Answer 32

y - y(hat)

Question 33

error = noise =

Answer 33

distance = residual

Question 34

residual =

Answer 34

observed y - predicted y

Question 35

outliers in y direction are

Answer 35

residuals (large)

Question 36

outliers in x direction are

Answer 36

influential

Question 37

data =

Answer 37

signal + noise

Question 38

r^2 =

Answer 38

variations explained by model/total variations

Question 39

total variations =

Answer 39

variation explained + unexplained