# Test Yourself

## Hint: do a 2x2 contingency table if you find this difficult..

A clinic considers that sperm are satisfactory if they fertilise >=50% of mature eggs.  A new test to predict satisfactory fertilisation was tested on semen samples from 200 couples.  One hundred and twenty samples gave a positive result and 100 of these couples achieved >=50% fertilisation.  By contrast among the couples whose semen failed the test only 20 achieved >=50% fertilisation. Indicate whether these statements are true or false.

### Question 1

The probability of a positive satisfactory fertilisation test result given a couple will actually  achieve a satisfactory fertilisation is 83%

### Question 2

The probability of a negative satisfactory fertilisation test result given a couple will not actually achieve satisfactory fertilisation is 85%

### Question 3

The probability that a couple will go onto achieve satisfactory fertilisation if they have a positive satisfactory fertilisation test result is 75%