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Suppose that the probability is \(.1\) that any given citrus tree will show measurable damage when the temperature falls to \(30^{\circ} \mathrm{F}\). If the temperature does drop to \(30^{\circ} \mathrm{F}\), what is the expected number of citrus trees showing damage in orchards of 2000 trees? What is the standard deviation of the number of trees that show damage?

Short Answer

Expert verified
Expected number of damaged trees: 200, Standard Deviation: 40

Step by step solution

01

Calculate Expected Value (Mean)

The expected value or mean for a binomial distribution can be calculated using the formula: \[ E(x) = np \] Where n is the number of experiments and p is the probability of success on each experiment. Therefore, \[ E(x) = 2000 * .1 = 200 \] Expected value or the mean is 200, which means that 200 trees are expected to show damage when the temperature falls to \(30^{\circ} \mathrm{F}\).
02

Calculate the Standard Deviation

The standard deviation for a binomial distribution can be calculated using the formula: \[ SD = \sqrt{np(1-p)} \] Where n is the number of experiments, p is the probability of success on each experiment. Here, \[ SD = \sqrt{2000 * .1 * (1-.1)} = 40 \] So, the standard deviation is 40 trees.
03

Interpret the Results

The expected number of trees showing damage is 200 with a standard deviation of 40 trees. This means that we can expect around 200 trees to show damage, but that number could realistically fall anywhere from 160 to 240 trees.

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Key Concepts

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

Expected Value
When tackling statistics problems, understanding the expected value is crucial. It represents the average outcome if an experiment were repeated many times. In the context of the citrus trees, expected value tells us how many trees, on average, we'd expect to show damage due to cold temperatures.

Using the formula for the expected value of a binomial distribution, which is \( E(x) = np \), where \( n \) is the total number of trials (trees), and \( p \) is the probability of a tree showing damage, we can calculate this average. In our example, with 2000 trees and a probability of 0.1, the calculation becomes \( E(x) = 2000 \times 0.1 = 200 \). Thus, on average, 200 out of 2000 citrus trees are expected to show damage at \(30^\circ F\). This value is highly practical as it helps orchard owners prepare and respond appropriately to cold weather conditions, anticipating potential damage to a portion of their trees.
Standard Deviation
Standard deviation is a statistics concept that measures the amount of variation or dispersion from the expected value. Think of it as an indicator of how spread out the results can be. This number can give us an idea of the reliability of the expected value. The lower the standard deviation, the closer the actual numbers tend to be to the mean or expected value. Conversely, a high standard deviation indicates a wide range of potential outcomes.

In the binomial distribution, the standard deviation is calculated with \( SD = \sqrt{np(1-p)} \). In our citrus tree example, this translates to \( SD = \sqrt{2000 \times 0.1 \times (1-0.1)} = 40 \). The standard deviation of 40 trees tells us that while we expect 200 trees to show damage, the actual number could generally differ by about 40 trees more or less due to natural variance.
Probability
Probability is a measure of the likelihood that a given event will occur. In statistical terms, it's expressed as a number between 0 and 1, with 0 indicating an impossible event and 1 representing a certainty. Probabilities are foundational in determining expected values and standard deviations in binomial distributions.

In the given exercise, the probability that a citrus tree will show damage when the temperature falls to \(30^\circ F\) is 0.1 (or 10%). This probability, while seemingly small, has significant repercussions when applied to a large number of trees, such as in an orchard with 2000 trees. By using this probability, we can forecast incidents and apply this knowledge to larger scales or different scenarios, such as predicting outcomes for different sizes of orchards or with varying probabilities of damage.

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