Cambridge International Mathematics

3 Strawberry plants are sprayed with a pesticide-fertiliser mix. The

data below give the yield of strawberries per plant for various

spray concentrations:

0 2 4 5 8

8 10 21 20 35

a Draw a scatter diagram for the data.

b Comment on the correlation between the variables.

c What is the significance of your answers inb?

d Find the equation of regression line for the data.

e Predict the number of strawberries per plant if the spray concentration is:

iii

f Give one reason why your answer toeiimay be invalid.

4 The whorls on a cone shell get broader as you go from the top of the shell towards the bottom.

Measurements from a shell are summarised in the following table:

Position of whorl,p 1 2 3 4 5 6 7 8

Width of whorl,wcm 0 : 7 1 : 2 1 : 4 2 : 0 2 : 0 2 : 7 2 : 9 3 : 5

a What are the dependent and independent variables?

b Obtain a scatter diagram for the data.

c Comment on the corrrelation between the variables.

d Find the linear regression model which best fits the data.

e If a cone shell has 14 whorls, what width do you expect

the 14 th whorl to have? How reliable do you expect this

prediction to be?

Review set 22B

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1 Traffic controllers want to find the association between the

average speedof cars in a city and theage of drivers. Devices

for measuring average speed were fitted to the cars of drivers

participating in a survey.

The results are shown in the scatter diagram.

a What is the independent variable?

b Describe the association between the variables.

c Is it sensible to find the linear regression line for these

variables? Why or why not?

2 Following an outbreak of theEbolavirus, a rare and deadly haemorrhagic fever, medical authorities

begin taking records of the number of cases of the fever. Their records are shown below.

Days after outbreak,n 2 3 4 5 6 7 8 9 10 11

Diagnosed cases,d 8 14 33 47 80 97 118 123 139 153

1 2 3 4 5 6 7 8

50

20 30 40 50 60 70 80 90

60

70

average speed

O age

Spray concentration ( ml per litre)x

3 ml per litre 10 ml per litre.

Two variable analysis (Chapter 22) 467

Yield ofstrawberries per plant (, y)

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Y:\HAESE\IGCSE01\IG01_22\467IGCSE01_22.CDR Tuesday, 18 November 2008 11:15:54 AM PETER