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Suppose \(F(x)\) is the cumulative distribution function for heights (in meters) of trees in a forest. (a) Explain in terms of trees the meaning of the statement \(F(7)=0.6\) (b) Which is greater, \(F(6)\) or \(F(7)\) ? Justify your answer in terms of trees.

Short Answer

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(a) 60% of trees are 7 meters tall or shorter. (b) \( F(6) < F(7) \) because \( F(x) \) is non-decreasing.

Step by step solution

01

Understanding Cumulative Distribution Function

The cumulative distribution function (CDF) \( F(x) \) of a random variable provides the probability that the variable will take a value less than or equal to \( x \). In this context, \( F(x) \) represents the probability that the height \( X \) of a tree in the forest is less than or equal to \( x \) meters.
02

Interpreting the Statement \( F(7)=0.6 \)

The statement \( F(7) = 0.6 \) means that there is a 60% probability that a randomly selected tree in the forest will have a height of 7 meters or less. This implies that 60% of the trees in the forest are 7 meters tall or shorter.
03

Comparing \( F(6) \) and \( F(7) \)

Since \( F(x) \) is a cumulative distribution function, it is a non-decreasing function. Therefore, as \( x \) increases, \( F(x) \) cannot decrease. Consequently, \( F(6) \leq F(7) \). More intuitively, more trees (or at least the same number) will have a height of 7 meters or less compared to those that are 6 meters or less.
04

Conclusion for Comparison

Since \( F(x) \) is non-decreasing, and given \( F(7) = 0.6 \), it is likely that \( F(6) < F(7) \) unless the distribution is constant over this range. The specific value of \( F(6) \) isn't given, but typically, \( F(6) < 0.6 \), meaning fewer than 60% of trees are 6 meters tall or shorter.

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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 ranges from 0 to 1, where 0 means the event is impossible and 1 means it is certain. In terms of our tree example, when we say that \( F(7) = 0.6 \), this indicates a probability of 0.6, or 60%, that a randomly selected tree from the forest is 7 meters or shorter. This probability helps us understand the proportion of trees that fall below a certain height threshold.
Random Variable
A random variable is a variable whose possible values are numerical outcomes of a random phenomenon. It is a key concept in probability and statistics. In our example, the height of the trees in the forest can be considered a random variable, usually denoted by \( X \). The value that \( X \) takes can vary depending on which tree we select. The cumulative distribution function, \( F(x) \), provides a statistical way to describe the distribution of these heights by giving probabilities for the different possible outcomes.
Non-Decreasing Function
A non-decreasing function is a type of function where the value does not decrease as the input increases. This means that as you move along the function's domain from left to right, the function either stays the same or increases. The Cumulative Distribution Function (CDF), \( F(x) \), is always a non-decreasing function. This is because, by definition, as the variable \( x \) increases, the probability of the random variable being less than or equal to \( x \) should either stay constant or increase. In our context, \( F(6) \leq F(7) \) because more trees (or at least the same number) will have a height of 7 meters or less than those that are 6 meters or less.
Statistics
Statistics is a field of study concerned with collecting, analyzing, interpreting, presenting, and organizing data. It provides tools to handle data and infer conclusions about them. In the context of the exercise, statistics highlights how the cumulative distribution function characterizes the probability distribution of tree heights in the forest. By analyzing \( F(x) \), we gain insights into how the trees' heights are spread out, enabling us to make informed decisions or predictions about the population of trees, such as determining the heights below which a certain percentage of trees fall. This helps in understanding natural phenomena, planning resources in forestry, or even ensuring biodiversity.

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