Which of the following experiments have equally likely outcomes? Explain.

(A) A driver attempts to start a car. The car starts or does not start.

(B) Tossing a fair coin once.

(C) Rolling a fair 6-sided die.

(D) Choosing a marble randomly from a bag that contains 3 red marbles and 7 blue marbles.

(E) A baby is born. It is a boy or a girl.

(A) Not equally likely.

The car is designed to start, so normally P(starts) is much higher than P(does not start).

The two outcomes are not equally likely.

(B) Equally likely.

Heads and tails each have probability $\frac{1}{2}$.

(C) Equally likely.

Each of the 6 faces has probability $\frac{1}{6}$.

(D) Not equally likely. Two colour-outcomes:

$$P(\text{red}) = \frac{3}{10} \text{ and } P(\text{blue}) = \frac{7}{10}$$

(E) Equally likely.

The biological ratio is close to 1 : 1, so for most purposes we treat it as equally likely = $\frac{1}{2}$.