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Suppose the average credit card debt for households currently is \(\$ 9500\) with a standard deviation of \(\$ 2600\). a. Using Chebyshev's theorem, find at least what percentage of current credit card debts for all households are between i. \(\$ 4300\) and \(\$ 14,700\) ii. \(\$ 3000\) and \(\$ 16,000\) :b. Using Chebyshev's theorem, find the interval that contains credit card debts of at least \(89 \%\) of all households.

Short Answer

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i. At least 75% of current credit card debts are between $4300 and $14700. ii. At least 84% of current credit card debts are between $3000 and $16000. An interval that contains credit card debts of at least 89% of all households is between $1700 and $17300.

Step by step solution

01

Calculate the percentage for the first interval

For the first question, we use the Chebyshev's theorem. The formula is \(1 - (1/k^2)\), where k is the number of standard deviations away from the mean. Here we have the mean (\$9500) and the standard deviation (\$2600). We need to find k for the intervals from \$4300 to \$14700. So, \( k1 = (9500-4300)/2600 = 2 \) and \( k2 = (14700-9500)/2600 = 2 \). By plugging the value of k into the theorem, we get the percentage (1-(1/4)) *100 = 75%.
02

Calculate the percentage for the second interval

For the second interval, we again need to calculate k for the intervals from \$3000 to \$16000. Here, \( k1 = (9500-3000)/2600 = 2.5 \) and \( k2 = (16000-9500)/2600 = 2.5 \). By plugging the value of k into the theorem, we get the percentage (1-(1/6.25)) *100 = 84%.
03

Calculate the interval for a given percentage

To find the interval that contains at least 89% of all households, we need to rearrange the formula and solve for k. The formula becomes \( k = sqrt(1/(1-0.89))\), which gives k approximately as 3. So, the interval would be from \$9500-3*\$2600= \$1700 to \$9500+3*\$2600= \$17300.

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Key Concepts

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

Credit Card Debt Statistics
Credit card debt statistics provide valuable insights into the spending habits and financial burdens of households. Understanding these statistics is essential for both personal financial planning and broader economic analysis. The data includes the average amount of debt, which can highlight the financial stress experienced by many, as well as the variation in debt levels among different families.

For example, if the average credit card debt for households is $9500, this number alone provides a baseline understanding. However, it's also important to consider the standard deviation, which will show how much individual household debts differ from this average. If there is a high standard deviation, it indicates a wide range of debt amounts, which suggests that some households are vastly more indebted than others.

By examining these statistics, policymakers and financial advisors can develop strategies to assist consumers in reducing their debt, ensuring the economy is healthier, and households are more financially secure.
Standard Deviation
Standard deviation is a statistic that measures the amount of variability or dispersion in a set of values. In the context of credit card debt statistics, it helps us understand how spread out household debts are around the average debt value.

In mathematical terms, standard deviation is computed by taking the square root of the average of the squared deviations from the mean. The formula is given by \[ \text{Standard Deviation} = \sqrt{\frac{1}{N} \sum_{i=1}^N (x_i - \mu)^2} \] where \( x_i \) is each value in the dataset, \( \mu \) is the mean of the dataset, and \( N \) is the number of values in the dataset.

In our example, a standard deviation of \(2600 implies that the debt levels of households tend to differ from the average debt of \)9500 by $2600, on average. The standard deviation can thus help in understanding how typical or atypical a particular debt value might be compared to the entire dataset as well as assist in planning for financial risk management.
Percentage Calculation
Percentage calculation is crucial in various financial contexts, especially when using concepts like Chebyshev's theorem. This theorem allows us to calculate the minimum proportion of data points that lie within a certain number of standard deviations from the mean.

To find the percentage of data that falls within a specific range, we use the formula: \[ 1 - \left( \frac{1}{k^2} \right) \]where \( k \) is the number of standard deviations that cover the interval. Multiplying the result by 100 gives the percentage of data within that range.

For example, if \( k = 2 \), the percentage of data within this range can be calculated as \[ 1 - \left( \frac{1}{2^2} \right) = 0.75 \]Thus, at least 75% of the data falls within two standard deviations of the mean. This method is especially useful in non-normal distributions, providing a way to understand data dispersion without assuming a specific distribution shape.

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Most popular questions from this chapter

The following data give the numbers of new cars sold at a dealership during a 20 -day period. \(\begin{array}{lrlrlllll}8 & 5 & 12 & 3 & 9 & 10 & 6 & 12 & 8 \\\ 4 & 16 & 10 & 11 & 7 & 7 & 3 & 5 & 9\end{array}\) a. Calculate the values of the three quartiles and the interquartile range. Where does the value of 4 lie in relation to these quartiles? b. Find the (approximate) value of the 25 th percentile. Give a brief interpretation of this percentile. c. Find the percentile rank of 10 . Give a brief interpretation of this percentile rank.

The following data represent the total points scored in each of the NFL championship games played from 2000 through 2009 in that order. \(\begin{array}{lllllllllll}39 & 41 & 37 & 69 & 61 & 45 & 31 & 46 & 31 & 50\end{array}\)

Prepare a box-and-whisker plot for the following data: \(\begin{array}{llllllll}36 & 43 & 28 & 52 & 41 & 59 & 47 & 61 \\ 24 & 55 & 63 & 73 & 32 & 25 & 35 & 49 \\ 31 & 22 & 61 & 42 & 58 & 65 & 98 & 34\end{array}\)

When studying phenomena such as inflation or population changes that involve periodic increases or decreases, the geometric mean is used to find the average change over the entire period under study. To calculate the geometric mean of a sequence of \(n\) values \(x_{1}, x_{2}, \ldots, x_{n}\), we multiply them together and then find the \(n\) th root of this product. Thus $$ \text { Geometric mean }=\sqrt[n]{x_{1} \cdot x_{2} \cdot x_{3} \cdot \ldots \cdot x_{n}} $$ Suppose that the inflation rates for the last five years are \(4 \%, 3 \%, 5 \%, 6 \%\), and \(8 \%\), respectively. Thus at the end of the first year, the price index will be \(1.04\) times the price index at the beginning of the year, and so on. Find the mean rate of inflation over the 5 -year period by finding the geometric mean of the data set \(1.04,1.03,1.05,1.06\), and \(1.08 .\) (Hint: Here, \(n=5, x_{1}=1.04, x_{2}=1.03\), and so on. Use the \(x^{1 / n}\) key on your calculator to find the fifth root. Note that the mean inflation rate will be obtained by subtracting 1 from the geometric mean.)

Can the standard deviation have a negative value? Explain.

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