All Leaving Cert Mathematics posts
• 2014 HL Maths question 8??! vanilllacookie

Does anyone understand why 0.003 is filled in the first box when the question says 0.3% of the population has the disease?

https://www.studyclix.ie/Subjects/Leaving-Certificate/Higher/Mathematics/Probability

its the second question

1. Blaithin

In order to change a decimal to a percentage, we multiply by 100. Therefore when we are given a percentage and want to change it back to a decimal, we divide by 100. They tell us that there is a 0.3% chance of a person having the disease. In probability we prefer to work with decimals, so we divide by 100 to get 0.003.

If you think about it, when we are told that there is a 0.3% chance that a person has this disease, it really means that for every 100 people we test, 0.3 people will have the disease. If we multiply both these numbers by 10, we see that 3 out of every 1000 people tested will have the disease, which when written as a decimal is 0.003.

0.003 is just another way of writing 0.3%.

I hope this explanation is clear. :)