Question

In Exercises \(\mathrm{P} .95\) to \(\mathrm{P} .99,\) determine whether the process describes a binomial random variable. If it is binomial, give values for \(n\) and \(p .\) If it is not binomial, state why not. Count the number of sixes in 10 dice rolls.

Short answer

The given process describes a binomial random variable. The number of trials \(n\) is 10 and the probability of success \(p\) is 1/6.

Step-by-step solution

Identify the Type of Variable

Examine the question and the conditions for a binomial random variable. In this case, the process of rolling a die 10 times and counting the number of sixes meets the conditions of a binomial random variable.

Find the trial count (n)

The number of trials, \(n\), refers to how many times the experiment is repeated. In this scenario, the die is rolled 10 times, so \(n = 10\).

Find the probability of success (p)

The probability of success, \(p\), is the likelihood of the desired outcome. A six has a 1-in-6 chance of being rolled on a die, this makes the probability of success \(p = 1/6\).

Key concepts

Probability of Success

Understanding the probability of success is fundamental in calculating the binomial random variable. It represents the likelihood of achieving the desired outcome in a single trial. In the context of dice rolls, if the desired outcome is rolling a six, we consider the structure of a regular die. A standard die has six faces, each with an equal chance of landing face up. Thus, the probability of rolling a six is one out of six possible outcomes, or
\[\begin{equation} p = \frac{1}{6}. \end{equation}\]
The concept rests on the assumption that each roll of the die is independent, meaning the result of one roll does not affect the outcome of the next roll. It's essential to grasp that the probability of success remains constant throughout all trials in a binomial experiment. This consistent probability is what underpins the calculations for binomial distributions and sets the stage for determining the likelihood of various scenarios involving multiple trials.

Trial Count

The trial count, denoted by 'n,' is another pillar in the study of binomial random variables. This numeric value represents the total number of independent trials conducted in the experiment. In the scenario of rolling a die, each roll is considered a separate trial. When evaluating whether an activity qualifies as a binomial random variable, not only should the individual trials be independent, but the number of trials should also be fixed beforehand.

In the given exercise, the die is rolled 10 times, which sets our trial count as
\[\begin{equation} n = 10. \end{equation}\]
Having a predetermined trial count is crucial; it enables the calculation of the distribution of outcomes and probabilities that govern the statistical analysis of binomial experiments. This fixed trial count allows for a structured approach to predict various outcomes based on the defined probability of success.

Binomial Distribution Conditions

Defining Characteristics

Binomial distribution conditions are specific requirements that a process must meet to be considered a binomial random variable. The conditions include a fixed number of trials, binary outcomes (success or failure), identical probability of success for each trial, and independence between trials. In our dice-rolling example, these conditions are satisfied as follows:

• There is a fixed number of trials: 10 dice rolls.
• Each roll results in a success (rolling a six) or a failure (rolling any other number).
• The probability of rolling a six is constant at \[\begin{equation} p = \frac{1}{6} \end{equation}\] across all trials.
• Rolling a die multiple times does not influence the result of subsequent rolls, implying that the trials are independent.

Variability of Outcomes

Even with all conditions met, the variability of the outcomes in a binomial distribution is expected. In other words, while the overall pattern of outcomes over many repetitions will match the binomial distribution, individual series of 10 dice rolls may yield different numbers of successes. Students often struggle with understanding why they don't always get the 'expected' number of sixes (which would be the mean of the distribution), but it's important to comprehend that probability describes the likelihood over the long term and not precise predictions for each experiment. By grasping these conditions and the concept of variability, students can better interpret binomial distributions and utilize them in practical scenarios, enhancing their statistical literacy.