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Suppose \(1.5 \%\) of the antennas on new Nokia cell phones are defective. For a random sample of 200 antennas, find the probability that: a. None of the antennas is defective. b. Three or more of the antennas are defective.

Short Answer

Expert verified
a) Probability that none are defective is 0.049. b) Probability that three or more are defective is 0.578.

Step by step solution

01

Understand the problem

We are given that 1.5% of the antennas are defective. We need to calculate the probability of having 0 defective antennas and the probability of having 3 or more defective antennas in a sample of 200 antennas. This is a binomial probability problem where we have a certain number of trials (200 antennas), two outcomes (defective or not defective), and a known probability of success (antenna being defective, p = 0.015).
02

Set up parameters for the binomial distribution

In a binomial distribution, the number of trials is denoted as \(n = 200\), and the probability of success (defective antenna) is \(p = 0.015\). The number of defective antennas we are interested in, \(X\), can range from 0 to 200.
03

Use binomial probability formula to solve part (a)

To find the probability that none of the antennas is defective, we use the binomial probability formula for \(k = 0\).\[P(X = 0) = \binom{n}{k} p^k (1-p)^{n-k} = \binom{200}{0} (0.015)^0 (1-0.015)^{200}\]Where \(\binom{200}{0} = 1\) and \((0.015)^0 = 1\). This simplifies to \((0.985)^{200}\).
04

Calculate the probability for part (a)

Calculate \((0.985)^{200}\) using a calculator or computational tool to obtain the probability that no antennas are defective:\[P(X = 0) \approx 0.049\]
05

Use binomial formula to solve part (b)

For part (b), we need to find the probability that at least 3 antennas are defective, i.e., \(P(X \geq 3)\). This can be calculated by 1 minus the probability of having 0, 1, or 2 defective antennas:\[P(X \geq 3) = 1 - (P(X = 0) + P(X = 1) + P(X = 2))\]Use the binomial formula for \(k = 1\) and \(k = 2\) to find these probabilities.
06

Calculate probability for part (b)

First find:\[P(X = 1) = \binom{200}{1} (0.015)^1 (1-0.015)^{199} \approx 0.149\]And:\[P(X = 2) = \binom{200}{2} (0.015)^2 (1-0.015)^{198} \approx 0.224\]Add these up along with \(P(X = 0)\):\[P(X = 0) + P(X = 1) + P(X = 2) \approx 0.049 + 0.149 + 0.224 = 0.422\]Finally calculate \(P(X \geq 3)\):\[P(X \geq 3) = 1 - 0.422 = 0.578\]
07

Final results

Using our calculations, we found that the probability that none of the antennas are defective is approximately 0.049, and the probability that three or more antennas are defective is approximately 0.578.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Probability
Probability is a fundamental concept in statistics that measures how likely an event is to occur. It's central to understanding how often we can expect certain outcomes in various scenarios. To calculate probability, we often use a formula that compares the number of successful outcomes to the total number of possible outcomes.

In the context of our exercise, we are examining the probability of defective antennas in Nokia cell phones. This involves determining how likely it is for a certain number of antennas to be defective in a sample. Knowing the probability helps in making informed decisions, predicting outcomes, and understanding risks. Probability is expressed as a number between 0 and 1, with 0 indicating an impossible event and 1 signifying a certain event.

Key concepts related to probability include:
  • Outcomes: Possible results of a scenario or experiment.
  • Events: One or more outcomes that form a specific result.
  • Success: The desired outcome, such as finding a defective antenna.
Understanding probability equips you with the tools to make predictions based on numerical data and trends.
Defective Items
Defective items refer to products that do not meet quality standards. In our context, a defective item is a Nokia cell phone antenna that fails to function as intended. Defective items are critical in quality control because they can directly affect customer satisfaction and company reputation.

In statistical terms, defective items are considered as 'successes' in a binomial distribution because the event of interest is identifying faults. Therefore, the probability of finding defective items within a batch or sample, such as in our problem, becomes crucial for industries.

Companies need to monitor the rate of defective items to:
  • Ensure product reliability and safety.
  • Minimize returns and repairs.
  • Maintain brand reputation.
Detecting and reducing the number of defective items often involves rigorous testing and analysis, just like in our exercise with Nokia cell phones, to keep defect rates at a minimum.
Statistical Analysis
Statistical analysis involves collecting and examining data sets to infer patterns and trends. It provides insights and supports decision-making processes by applying statistical tools and methodologies.

In our problem, statistical analysis is used to determine the probability distribution of defective antennas. We use the binomial distribution to model this scenario because it deals with two outcomes: defective or not defective.

Components of statistical analysis typically include:
  • Data Collection: Gathering sample data efficiently.
  • Data Analysis: Applying statistical methods, like the binomial formula, to summarize data.
  • Interpretation: Drawing conclusions and making predictions based on data results.
In the Nokia cell phone example, statistical analysis helps in making informed decisions about production and quality control based on the calculated probabilities of defects.
Nokia Cell Phones
Nokia is a well-known telecommunications company that manufactures cell phones and associated technologies. The brand has earned a reputation for durable and reliable devices, including its cellular phone antennas.

In our exercise, we're focusing on defective antennas of Nokia cell phones to understand the likelihood of defects in a random sample. Quality control is a vital aspect for companies like Nokia, which aims for high standards to maintain their market position. Analyzing defect rates helps in:

  • Improving manufacturing processes.
  • Enhancing product quality and design.
  • Reducing costs associated with returns and repairs.
Overall, Nokia's commitment to reliability means that they employ statistical tools to continually assess and improve their products. This ensures customer satisfaction, which is crucial for sustaining their brand identity in a competitive market.

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