Page 183 - BA2 Integrated Workbook - Student 2017
P. 183
Risk 2: probability
1.5 Using tables
In some exam questions you have to do some analytical work on the information
given before you can start to calculate probabilities. This is often easier if you use a
table to set out the different possibilities.
100 invoices for a company were selected. The invoices were analysed as follows:
New customer or existing customer
Worth $50 or more or less than $50
If we are told that
20 of the invoices related to first time customers, of these 18 were orders of less
than $50.
In total, 65 of all invoices were for over $50.
We can set up a table showing all the possibilities:
Under $50 $50 or over Total
New 18 2 20
Existing 17 63 80
Total 35 65 100
The table makes it easier to work out the probabilities of certain events:
The probability that an invoice selected at random was
from a new customer is 20/100 = 20%
for $50 or more is 65/100 = 65%.
The probability that an invoice from a new customer was for $50 or more is 2/20 =
10%
TYU 4
175
