Cambridge International Mathematics

c Using the results obtained by the marketing company, estimate the probability that the soap used

by a randomly selected person is:

i Just Soap ii Indulgence iii Silktouch?

Outcome Freq Rel Freq

0 heads 121

1 head

2 heads 109

Total

9 Two coins were tossed 489 times and thenumber of headsoccurring

at each toss was recorded. The results are shown opposite:

a Copy and complete the table given.

b Estimate the chance of the following events

occurring:

i 0 heads ii 1 head iii 2 heads.

10 At the Annual Show the toffee apple vendor estimated that three times as many people preferred red

toffee apples to green toffee apples.

Colour Freq Rel Freq

Green 361

Red

Total

a If 361 people wanted green toffee apples, estimate how many wanted

red.

b Copy and complete the table given.

c Estimate the probability that the next customer will ask for:

i a green toffee apple ii a red toffee apple.

Ticket Type Freq Rel Freq

Adult 3762

Concession 1084

Child 389

Total

11 The tickets sold for a tennis match were recorded as people entered

the stadium. The results are shown:

a How many tickets were sold in total?

b Copy and complete the table given.

c If a person in the stadium is selected at random, estimate the

probability that the person bought a Concession ticket.

Councillor Freq Rel Freq

Mr Tony Trimboli 2167

Mrs Andrea Sims 724

Mrs Sara Chong 2389

Mr John Henry

Total

12 The results of a local Council election are shown in the table.

It is known that 6000 people voted in the election.

a Copy and complete the table given.

b Estimate the chance that a randomly selected person

from this electorate voted for a female councillor.

Two-way tablesare tables which compare two categorical variables. They usually result from a survey.

For example, the year 10 students in a small school were tested to determine their ability in mathematics.

The results are summarised in the two-way table shown:

Boy Girl

Good at maths 17 19

Not good at maths 8 12 there are 12 girls who are not good at maths.

PROBABILITIES FROM TWO-WAY TABLES

[10.2, 10.6]

C

In this case the variables areability in mathsandgender.

We can use these tables to estimate probabilities.

510 Probability (Chapter 25)

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Y:\HAESE\IGCSE01\IG01_25\510IGCSE01_25.CDR Monday, 27 October 2008 2:30:47 PM PETER