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According to the Insurance Institute of America, a family of four spends between \(\$ 400\) and \(\$ 3,800\) per year on all types of insurance. Suppose the money spent is uniformly distributed between these amounts. a. What is the mean amount spent on insurance? b. What is the standard deviation of the amount spent? c. If we select a family at random, what is the probability they spend less than \(\$ 2,000\) per year on insurance? d. What is the probability a family spends more than \(\$ 3,000\) per year?

Short Answer

Expert verified
Mean: $2100; Standard Deviation: $980.58; P(<$2000): 0.471; P(>$3000): 0.235.

Step by step solution

01

Understand the Uniform Distribution

The uniform distribution is a type of probability distribution in which every outcome is equally likely. In this problem, the amount spent is uniformly distributed between $400 and $3,800.
02

Calculate the Mean

For a uniformly distributed variable between two values \(a\) and \(b\), the mean \(\mu\) is calculated using the formula: \[ \mu = \frac{a + b}{2} \]. Substituting the given values, \(a = 400\) and \(b = 3800\), we find: \[ \mu = \frac{400 + 3800}{2} = 2100 \].
03

Compute the Standard Deviation

The standard deviation \(\sigma\) of a uniform distribution is given by: \[ \sigma = \frac{b - a}{\sqrt{12}} \]. Using \(a = 400\) and \(b = 3800\), \[ \sigma = \frac{3800 - 400}{\sqrt{12}} = \frac{3400}{\sqrt{12}} \approx 980.58 \].
04

Calculate Probability for Spending Less than $2,000

To find the probability that a family spends less than \(2000, compute the fraction of the interval \([400, 3800]\) that lies below 2000. The length of the interval where spending is less than \)2000 is \(2000 - 400 = 1600\). Calculate the probability as: \[ P(X < 2000) = \frac{1600}{3400} \approx 0.471 \].
05

Calculate Probability for Spending More than $3,000

To find the probability that a family spends more than $3000, calculate the length of the interval \([3000, 3800]\), which is \(3800 - 3000 = 800\). The probability is:\[ P(X > 3000) = \frac{800}{3400} \approx 0.235 \].

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Key Concepts

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

Mean Calculation
In understanding uniform distribution for a given range, the first step involves calculating the mean, which also represents the average of that distribution. It tells us the central tendency or the midpoint for a uniformly distributed random variable.

For a uniform distribution within a range from a minimum value, \(a\), to a maximum value, \(b\), the mean is determined using the formula:
  • \( \mu = \frac{a + b}{2} \)
This straightforward formula encapsulates the concept that, for uniform distribution, every point within the given range is equally likely. In this example, with spending ranging from \(\\(400\) to \(\\)3,800\), the mean expenditure is calculated as:
  • \( \mu = \frac{400 + 3800}{2} = 2100 \)
Hence, a family of four is expected to spend, on average, \(\$2,100\) annually on insurance.
Standard Deviation
Standard deviation is a measure of the spread of data points in a distribution. In uniform distribution, it explains how much the individual points may deviate from the mean within a specified range.

For a uniform distribution, the formula for standard deviation, \(\sigma\), is given by:
  • \( \sigma = \frac{b - a}{\sqrt{12}} \)
In the context of our example, where the insurance expenditure ranges from \(\\(400\) to \(\\)3,800\), the standard deviation is calculated as:
  • \( \sigma = \frac{3800 - 400}{\sqrt{12}} \approx 980.58 \)
This figure indicates that the spending by each family is distributed quite widely around the mean (\(\$2,100\)), reflecting the variability in expenditure levels.
Probability
Probability in the context of uniform distribution allows us to calculate the likelihood of an event occurring within a specific interval. For this distribution, each interval of the same length has an equal chance of occurring.

The probability that a randomly selected family spends less than \(\\(2,000\) is determined by the fraction of the total interval where the spending is below \(\\)2,000\).
  • The interval from \(\\(400\) to \(\\)2,000\) has a length of \(1,600\).
  • The total interval \([400, 3800]\) has a length of \(3,400\).
Thus the probability is:
  • \( P(X < 2000) = \frac{1600}{3400} \approx 0.471 \)
Similarly, the probability of spending more than \(\$3,000\) is calculated by the length of the interval \([3,000, 3,800]\), which is \(800\), thus:
  • \( P(X > 3000) = \frac{800}{3400} \approx 0.235 \)
These probabilities provide insights into the spending behaviors of families within the given range.
Insurance Expenditure
Insurance expenditure refers to the amount of money a family spends on various types of insurance each year. Understanding the distribution of this expense among families can provide insights into average financial commitments and potential savings opportunities.

Given the uniformly distributed expenditure data, we ascertain the mean and standard deviation to understand the average and variability in spending. Moreover, probabilities help predict behaviors in spending.
  • If the mean is \(\\(2,100\), it indicates a central point of expenditure.
  • A standard deviation near \(\\)980.58\) shows potential large swings from the mean, providing a snapshot of spending inconsistency.
  • Probabilities show the likelihood of a family spending within a certain range.
It's crucial in everyday decision-making for budgeting and can influence financial planning for families wanting to optimize their insurance purchases. By understanding these statistics, families can better position themselves to either maintain or adjust their insurance plans.

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Most popular questions from this chapter

Shaver Manufacturing Inc. offers dental insurance to its employees. A recent study by the human resource director shows the annual cost per employee per year followed the normal probability distribution, with a mean of \(\$ 1,280\) and a standard deviation of \(\$ 420\) per year. a. What is the probability that annual dental expenses are more than \(\$ 1,500 ?\) b. What is the probability that annual dental expenses are between \(\$ 1,500\) and \(\$ 2,000 ?\) c. Estimate the probability that an employee had no annual dental expenses. d. What was the cost for the \(10 \%\) of employees who incurred the highest dental expense?

A uniform distribution is defined over the interval from 6 to 10. a. What are the values for \(a\) and \(b\) ? b. What is the mean of this uniform distribution? c. What is the standard deviation? d. Show that the total area is 1.00 . e. Find the probability of a value more than 7 . f. Find the probability of a value between 7 and \(9 .\)

A normal population has a mean of 20.0 and a standard deviation of \(4.0 .\) a. Compute the \(z\) value associated with 25.0 . b. What proportion of the population is between 20.0 and \(25.0 ?\) c. What proportion of the population is less than \(18.0 ?\)

The distribution of the number of viewers for the American Idol television show follows a normal distribution with a mean of 29 million and a standard deviation of 5 million. What is the probability next week's show will: a. Have between 30 and 34 million viewers? b. Have at least 23 million viewers? c. Exceed 40 million viewers?

The closing price of Schnur Sporting Goods Inc. common stock is uniformly distributed between \(\$ 20\) and \(\$ 30\) per share. What is the probability that the stock price will be: a. More than \(\$ 27 ?\) b. Less than \(\$ 24 ?\)

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