chapter 4

Question 1

when is it best to use scatter diagrams?

Answer 1

when it is bivariate data

Question 2

what do scatter diagrams show?

Answer 2

whether 2 sets of data are associated

Question 3

what is the variable that you change?

Answer 3

the explanatory (independent) variable

Question 4

what is the other variable called?

Answer 4

the response (dependant) variable

Question 5

when drawing a scatter diagram where does the explanatory variable go?

Answer 5

on the horizontal (x) axis

Question 6

what is correlation?

Answer 6

an association between 2 variables that shows an increasing or decreasing trend

Question 7

if the points are very scattered about a straight line, what type of correlation is this?

Answer 7

weak linear correlation

Question 8

if the points formed make a curved line, what type of correlation is this?

Answer 8

non- linear correlation

Question 9

when is a causal relationship formed?

Answer 9

when a change in one variable directly causes a change in another variable, there is a causal relationship between them

Question 10

when do we draw a line of best fit?

Answer 10

if the scatter diagram shows linear correlation

Question 11

where should the line of best fit go through?

Answer 11

the mean point

Question 12

what is interpolation?

Answer 12

using a line of best fit to estimate data values from within the range of data

Question 13

what is extrapolation?

Answer 13

using a line of best fit to estimate data values from outside the range of data

Question 14

when are values estimated by extrapolation less reliable?

Answer 14

when they are further away from the line of best fit

Question 15

what is the line of best fit also known as?

Answer 15

the regression line

Question 16

what does the gradient (a) show?

Answer 16

the rate of increase of the response variable in relation to the explanatory variable

Question 17

what does the y intercept (b) show?

Answer 17

the value of the response variable when the explanatory variable is 0

Question 18

what does Spearman’s rank correlation coefficient show?

Answer 18

measures the strength of the correlation between 2 sets of data

Question 19

if r is close to 1…

Answer 19

strong positive correlation

Question 20

if r is 0…

Answer 20

no correlation

Question 21

if r is close to -1…

Answer 21

there is strong negative correlation

Question 22

what do you need to do first to calculate Spearman’s rank?

Answer 22

need to rank the data in each set

Question 23

what does Pearson’s product test for?

Answer 23

linear correlation

Question 24

what does Pearson’s product measure?

Answer 24

the strength of linear correlation between 2 sets of data

Question 25

what does Pearson’s product tell us?

Answer 25

how far the data points are from the linear regression line

Question 26

what type of data is Spearman’s rank most suitable for?

Answer 26

non-linear correlation