Stats Probability Question

Question

A colony of laboratory rats contains 18 white rats and 7 spotted rats. What is the probability of randomly selecting a white rat from this colony?

Answer 1

There are 18 white rats in this situation and 25 rats total. If you were to randomly select a rat, then you would have a 18/25 chance of selecting a white rat. That is a probability of 0.72.

Answer 2

There are a total of 25 rats (18 whites and 7 spotted).

P(White Rat) = 18/25 = 0.72

The probability of selecting a white rat from the colony is 0.72.

Answer 3

P_{(A)= n(A)/n(S)}

_{P(A)= The probability of Event A}

_{n(A)= The number of favorable outcome. In other words, the number of possibilities that meet your condition.}

_{n(S)= Total number of events in same sample space. In other words, it is the number of equally likely possibilities.}

_{So for this problem, we know the number of white rats (18) and number of spotted rats (7). If we add them together we get 25. That is the number of equally likely possibilities of selecting any rat. Now, the question is asking for the probability of selecting a white rat.}

1. n(A)= 18. This is how many white rats there are total that meet the number of possibilities within our condition of selecting a white rat.
2. n(S)= 25. Total number of rats in the sample to give us the equally likely possibilities in our probability. So now, we just plug into the formula: 18/25= 0.72 probability of selecting a white rat.