Question

If you were to roll a fair die 1,000 times, about how many sixes do you think you would observe? What is the probability of observing a six when a fair die is rolled?

Short answer

You are expected to roll a six approximately 167 times out of 1,000 rolls, and the probability of rolling a six in a single roll of a fair die is approximately 0.167 or 1/6.

Step-by-step solution

Calculate Expected Number of Sixes

To calculate the expected number of times a six will be rolled, multiply the total number of trials by the likelihood of a six being rolled in a single trial. The total number of trials is 1,000, and the probability of rolling a six once is 1/6. So, \( 1000 * \frac{1}{6} = 166.67 \). Therefore, a six is expected to come up approximately 167 times.

Calculate Probability of Rolling a Six

Since a die is a fair die with six equally likely outcomes, the probability of rolling a six is simply 1/6 or approximately 0.167.

Key concepts

Expected Value

When rolling a fair die, the concept of 'expected value' becomes a pivotal tool in understanding what results we can anticipate over the long run. In essence, expected value is the average outcome or result you can expect after running an experiment a large number of times. It’s calculated by multiplying the value of each possible outcome by the probability of that outcome occurring, and then summing these products.

For instance, in the context of our dice-rolling exercise, we want to find out how many times we can expect to get a six if we roll the die 1,000 times. Each roll is independent, and the chance of landing a six is 1 in 6. Mathematically, the expected value (E) equals the total trials (n) times the probability (p) of getting a six, thus: \[ E = n \times p = 1000 \times \frac{1}{6} \.\] Simplifying this yields \[ E \approx 166.67 \.\] So we round this number to the nearest whole number, as we can't roll a fraction of a time. That means you can expect to roll a six approximately 167 times in 1000 rolls.

Fair Die

The term 'fair die' guarantees that all outcomes are equally likely. If you imagine a standard six-sided die, each face numbered 1 through 6, a fair die means each number has an equal chance of landing face up on any given roll. This is the foundation of probability theory where fair means unbiased, unweighted, and not tampered with, ensuring each number has an exact \( \frac{1}{6} \) chance of occurring.

To understand if a die is fair, we can perform a large number of rolls and record the outcomes. If the die is fair, the number of times each of the six numbers comes up should be roughly equal. In the case of the exercise, rolling the die 1,000 times provides a large enough sample size to get close to the theoretical probability. Trusting in the fairness of the die, we use it to further calculate the expected values and probabilities of different outcomes.

Trial Probability

Trial probability is another term for the likelihood of an event occurring in a single instance or trial. In a dice game, each roll is considered a trial, and the probability of an event, such as rolling a six, is determined by the number of favorable outcomes divided by the total number of possible outcomes. On a fair six-sided die, the probability of rolling any given number is \( \frac{1}{6} \) given that there is one favorable outcome and six possible outcomes.

The trial probability remains constant for each roll as long as the die is fair. This concept is crucial in calculating the expected number of times a particular outcome will occur after a series of trials, as well as in understanding that each roll is independent of the others. Regardless of what you rolled before, the trial probability for the next roll is always the same when dealing with a fair die.