To determine the probability of getting no head when three coins are tossed, we need to find the probability of the event where all coins result in tails.
Each coin has two possible outcomes: head or tail. When three coins are tossed, the total number of possible outcomes is given by:
\[2 \times 2 \times 2 = 2^3 = 8\]
This means there are 8 potential outcomes.
Among these outcomes, the only combination that results in no head (all tails) is TTT.
Thus, the number of favorable outcomes is 1 (TTT).
The probability of an event is calculated as the ratio of the number of favorable outcomes to the total number of possible outcomes:
\[P(\text{No Head}) = \frac{\text{Number of Favorable Outcomes}}{\text{Total Number of Outcomes}}\]
Substituting the values, we have:
\[P(\text{No Head}) = \frac{1}{8}\]
Therefore, the probability of getting no head when tossing three coins is \(\frac{1}{8}\).
Based upon the results of regular medical check-ups in a hospital, it was found that out of 1000 people, 700 were very healthy, 200 maintained average health and 100 had a poor health record.
Let \( A_1 \): People with good health,
\( A_2 \): People with average health,
and \( A_3 \): People with poor health.
During a pandemic, the data expressed that the chances of people contracting the disease from category \( A_1, A_2 \) and \( A_3 \) are 25%, 35% and 50%, respectively.
Based upon the above information, answer the following questions:
(i) A person was tested randomly. What is the probability that he/she has contracted the disease?}
(ii) Given that the person has not contracted the disease, what is the probability that the person is from category \( A_2 \)?