问题


There is a single choice question about high school statistics. Answer the question by replying A, B, C or D.
Question: The financial aid office at a state university conducts a study to determine the total student costs per semester. All students are charged $4500 for tuition. The mean cost for books is $350 with a standard deviation of $65. The mean outlay for room and board is $2800 with a standard deviation of $380. The mean personal expenditure is $675 with a standard deviation of $125. Assuming independence among categories, what is the standard deviation of the total student costs?
A. $24
B. $91
C. $190
D. $405
Answer:

答案

模型 模型答案 正确答案
金声玉亮2.0

D. $405
D
deepseekr1

To determine the standard deviation of the total student costs, we calculate the variances of the variable costs (books, room and board, and personal expenditures) since tuition is fixed and contributes no variance.

1. **Variances**:
- Books: \(65^2 = 4225\)
- Room and board: \(380^2 = 144,400\)
- Personal expenditure: \(125^2 = 15,625\)

2. **Total Variance**:
\(4225 + 144,400 + 15,625 = 164,250\)

3. **Standard Deviation**:
\(\sqrt{164,250} \approx 405.3\), which rounds to **405**.

The correct answer is **D. $405**.

Answer: D
D
gpto1 To determine the standard deviation of the total student costs, we'll consider the variability contributed by each independent category (excluding the constant tuition fee, which doesn't contribute to variability):

1. **Books**: Standard deviation = $65
2. **Room and Board**: Standard deviation = $380
3. **Personal Expenditure**: Standard deviation = $125

Since the categories are independent, the variance of the total cost is the sum of the variances of these categories:

\[
\text{Total Variance} = (65)^2 + (380)^2 + (125)^2 = 4225 + 144400 + 15625 = 164250
\]

The standard deviation of the total cost is the square root of the total variance:

\[
\text{Standard Deviation} = \sqrt{164250} \approx 405
\]

**Answer: D**
D
GPT-4o To find the standard deviation of the total student costs per semester, we need to take into account the standard deviations of the individual components and use the principle of the independence of random variables.

Given the standard deviations:
- Tuition: $0 (tuition is a fixed cost, hence no deviation)
- Books: $65
- Room and board: $380
- Personal expenditure: $125

Since the costs are independent, the variance of the total cost is the sum of the variances of each component. The variance is the square of the standard deviation.

Variance of books: \( 65^2 = 4225 \)
Variance of room and board: \( 380^2 = 144400 \)
Variance of personal expenditure: \( 125^2 = 15625 \)

Total variance: \( 0 + 4225 + 144400 + 15625 = 164250 \)

The standard deviation of the total cost is the square root of the total variance:

\[ \sqrt{164250} \approx 405.28 \]

Therefore, the closest answer is:

D. $405
D
llama3.1-70B-Instruct

D
D
llama3.1-405B-Instruct

D
The best answer is D.
D
DeepSeek-Coder-V2 C. $190 D
Qwen2-72B-Instruct C. $190 D
baichuan4 D D
doubao D. $405

The variance of the total is the sum of the variances of the individual components. The variance is the square of the standard deviation. For tuition, there is no variance as it is a fixed amount. The variance for books is $65^2 = 4225$, for room and board is $380^2 = 144400$, and for personal expenditure is $125^2 = 15625$. The sum of these variances is 164250. The standard deviation of the total is the square root of the variance, which is approximately $405$.
D
minimax To find the standard deviation of the total student costs, we need to consider the standard deviations of each category and the fact that the categories are independent. When independent variables are added, their variances (squared standard deviations) are summed to find the total variance. Then, the square root of the total variance gives the standard deviation of the sum.

The total cost is the sum of the individual costs for tuition, books, room and board, and personal expenditures. Since tuition is a fixed cost, it does not contribute to the variance of the total costs. We only need to consider the variance of the costs that have a standard deviation.

The variance for each category is the square of the standard deviation:

- Books: $350^2 = $122,500
- Room and board: $380^2 = $144,400
- Personal expenditure: $125^2 = $15,625

Now, we sum these variances:

Total variance = $122,500 + $144,400 + $15,625 = $282,525

Finally, we take the square root of the total variance to find the standard deviation of the total costs:

Standard deviation = √$282,525 ≈ $531.57

However, this result is not among the options provided. It seems there might be a mistake in the options or in the calculation. Let's recheck the calculation:

- Books: $350^2 = $122,500
- Room and board: $380^2 = $144,400
- Personal expenditure: $125^2 = $15,625

Total variance = $122,500 + $144,400 + $15,625 = $282,525

Standard deviation = √$282,525 ≈ $531.57

The calculation is correct, but the result does not match any of the provided options. Given the options, none of them is correct based on the calculation. However, if we were to choose the closest answer, it would be:

D. $405

This is not the correct answer based on the calculation, but it is the closest to the calculated standard deviation of $531.57. There might be a mistake in the question or the options provided.
D
kimi To find the standard deviation of the total student costs, we can use the property that the variance of the sum of independent random variables is the sum of their variances. Since the standard deviation is the square root of the variance, we can calculate the variance of the total cost and then take the square root to find the standard deviation.

The variance of each category is the square of the standard deviation for that category.

For books:
Variance (books) = Standard deviation (books)^2 = $65^2 = $4225

For room and board:
Variance (room and board) = Standard deviation (room and board)^2 = $380^2 = $144400

For personal expenditure:
Variance (personal expenditure) = Standard deviation (personal expenditure)^2 = $125^2 = $15625

Now, we add the variances of each category to find the total variance:
Total variance = Variance (books) + Variance (room and board) + Variance (personal expenditure)
Total variance = $4225 + $144400 + $15625 = $165250

The standard deviation of the total student costs is the square root of the total variance:
Standard deviation (total) = √Total variance = √$165250

Now, let's calculate the square root of $165250:
Standard deviation (total) ≈ $406.04

The closest answer to our calculated standard deviation is:
D. $405
D
wenxinyiyan D. $405

Explanation:

Let's denote the four categories of costs as follows:

* Tuition: $4500 (this is a fixed cost, so it has no variance or standard deviation)
* Books: mean = $350, standard deviation = $65
* Room and Board: mean = $2800, standard deviation = $380
* Personal Expenditure: mean = $675, standard deviation = $125

Since the categories are assumed to be independent, the variance of the total cost is the sum of the variances of each category. The standard deviation is then the square root of this total variance.

Variance of Books = $65^2 = 4225
Variance of Room and Board = $380^2 = 144400
Variance of Personal Expenditure = $125^2 = 15625

Total Variance = 4225 + 144400 + 15625 = 164250

Standard Deviation of Total Cost = sqrt(164250) ≈ $405
D
zhipu To determine the standard deviation of the total student costs, we need to consider the standard deviations of each category and the fact that the costs are independent. The formula for the standard deviation of the sum of independent random variables is:

\[ \sigma_{total} = \sqrt{\sigma_1^2 + \sigma_2^2 + \sigma_3^2} \]

Here, the standard deviations are:
- Tuition: This is a fixed cost with no variability, so its standard deviation is \( \sigma_1 = 0 \).
- Books: \( \sigma_2 = 65 \)
- Room and board: \( \sigma_3 = 380 \)
- Personal expenditure: \( \sigma_4 = 125 \)

Plugging these values into the formula:

\[ \sigma_{total} = \sqrt{0^2 + 65^2 + 380^2 + 125^2} \]
\[ \sigma_{total} = \sqrt{0 + 4225 + 144400 + 15625} \]
\[ \sigma_{total} = \sqrt{164250} \]
\[ \sigma_{total} \approx 405.15 \]

Thus, the closest answer to our calculation is:

D. $405

So, the answer is D.
D
gpto1 To determine the standard deviation of the total student costs, we'll consider the variability contributed by each independent category (excluding the constant tuition fee, which doesn't contribute to variability):

1. **Books**: Standard deviation = $65
2. **Room and Board**: Standard deviation = $380
3. **Personal Expenditure**: Standard deviation = $125

Since the categories are independent, the variance of the total cost is the sum of the variances of these categories:

\[
\text{Total Variance} = (65)^2 + (380)^2 + (125)^2 = 4225 + 144400 + 15625 = 164250
\]

The standard deviation of the total cost is the square root of the total variance:

\[
\text{Standard Deviation} = \sqrt{164250} \approx 405
\]

**Answer: D**
D
deepseekv3 To find the standard deviation of the total student costs, we need to consider the variances of the individual costs and sum them up (since the categories are independent). The standard deviation is then the square root of the total variance.

The costs and their standard deviations are:
- Tuition: $4500 (with no standard deviation, as it is fixed)
- Books: $350, standard deviation = $65
- Room and board: $2800, standard deviation = $380
- Personal expenditure: $675, standard deviation = $125

The variances are:
- Books: \(65^2 = 4225\)
- Room and board: \(380^2 = 144400\)
- Personal expenditure: \(125^2 = 15625\)

The total variance is:
\[4225 + 144400 + 15625 = 164250\]

The standard deviation is the square root of the total variance:
\[\sqrt{164250} \approx 405\]

Thus, the correct answer is:

**D. $405**
D