Question

The relative frequency of Event A in an experiment is 20%. If the experiment is performed 40 times, how many times should you expect Event A to occur?

Enter your answer as a number, like this: 42

Answer 1

Explanation:

look at a die, for example.

the probabilty to roll a 6 is 1/6 (if all numbers truly have the same probability due to a perfectly balanced die).

so, you expect as a mean value that you have to roll the die 6 times to get one 6.

now in our general example :

20% = 1/5

so, we expect event A to happen once as a mean value every 5 attempts.

now we do 40 attempts. that means 8×5 sets of attempts.

and we therefore expect to see event A 8 times.