The two way table below contains some completely fictitious data on the the types of computers favoured by men and women.
|
|
Laptop |
Desktop |
Tablet |
Total |
|
Men |
31 |
17 |
40 |
88 |
|
Women |
12 |
42 |
17 |
71 |
|
Total |
43 |
59 |
57 |
159 |
Events A and B are independent if
(1)
For the table above take A as 'a person picked at random favours a desktop', and event B as 'a person picked at random is a woman'.
The probability that a person picked at random favours desktops is
and the probability that a person picked at random is a woman is
The number of women who favour desktops is 42 out of a total of 159, so the probability that a person picked at random is a woman favouring a desktop is
These probabilities do not satisfy condition (1) for indepence since