Problem Analysis #35

A.X-4.0 (72B) · Run 1

13.77s
3,481 toks
Problem Statement

A population is normally distributed with mean mm and standard deviation 55. From this population, a random sample of size 3636 is taken, and a 99%99\% confidence interval for the population mean mm is constructed using the sample mean. The resulting confidence interval is 1.2ma1.2 \leq m \leq a. Find the value of aa. (Here, ZZ denotes a standard normal random variable, and use P(Z2.58)=0.99\text{P}(|Z| \leq 2.58) = 0.99.) [3 points]Compute 10a10a.\

Ground Truth
55
Execution Trace
Reasoning Process

[THOUGHT] The confidence interval for the population mean mm is given by:

xˉZα/2(σn)mxˉ+Zα/2(σn)\bar{x} - Z_{\alpha/2} \left(\frac{\sigma}{\sqrt{n}}\right) \leq m \leq \bar{x} + Z_{\alpha/2} \left(\frac{\sigma}{\sqrt{n}}\right)

where:

  • xˉ\bar{x} is the sample mean,
  • Zα/2Z_{\alpha/2} is the critical value from the standard normal distribution,
  • σ\sigma is the population standard deviation,
  • nn is the sample size.

Given:

  • The confidence interval is 1.2ma1.2 \leq m \leq a,
  • The confidence level is 99%,
  • The critical value Zα/2=2.58Z_{\alpha/2} = 2.58,
  • The population standard deviation σ=5\sigma = 5,
  • The sample size n=36n = 36.

From the lower bound of the confidence interval:

xˉ2.58(536)=1.2\bar{x} - 2.58 \left(\frac{5}{\sqrt{36}}\right) = 1.2

First, calculate the standard error:

536=560.8333\frac{5}{\sqrt{36}} = \frac{5}{6} \approx 0.8333

Then, substitute the standard error into the equation:

xˉ2.58×0.8333=1.2\bar{x} - 2.58 \times 0.8333 = 1.2

Calculate 2.58×0.83332.58 \times 0.8333:

2.58×0.83332.1252.58 \times 0.8333 \approx 2.125

So:

xˉ2.125=1.2\bar{x} - 2.125 = 1.2

Solving for xˉ\bar{x}:

xˉ=1.2+2.125=3.325\bar{x} = 1.2 + 2.125 = 3.325

Now, use the sample mean to find the upper bound aa:

a=xˉ+2.58(536)a = \bar{x} + 2.58 \left(\frac{5}{\sqrt{36}}\right)

Substitute the sample mean and standard error:

a=3.325+2.125=5.45a = 3.325 + 2.125 = 5.45

Finally, compute 10a10a:

10a=10×5.45=54.510a = 10 \times 5.45 = 54.5

Since the final answer must be an integer:

545\boxed{545}

[/THOUGHT] [PYTHON]

Define the values

Z = 2.58 sigma = 5 n = 36 lower_bound = 1.2

Calculate the standard error

standard_error = sigma / (n ** 0.5)

Calculate the sample mean

sample_mean = lower_bound + Z * standard_error

Calculate the upper bound a

a = sample_mean + Z * standard_error

Calculate 10a

result = 10 * a print(int(result))

Tool Output
[PYTHON OUTPUT] 55 [/PYTHON OUTPUT]
Reasoning Process

[THOUGHT] Based on the Python output, the value of 10a10a is 5555. Therefore, the final answer is: 55\boxed{55}

Final Model Output
55

Comparative Analysis (P35) (Average across runs)

Avg Time Taken

EXAONE-4.0.1-32B (high)
636.4
K-EXAONE-236B-A23B
109.6
Llama-VARCO-8B-Instruct
80.1
HCX-007(high)
49.6
Deepseek-V3.2
47.8
Kanana-2-30B-Thinking
46.1
Gemini-3-Pro-Preview
24.4
Kanana-2-30B-Thinking-2601
22.1
Solar-Pro-2 (31B)(high)
16.4
Solar-Open-100B
14.7
Claude-Opus-4.5
13.8
A.X-4.0 (72B)
13.8
Grok-4.1-fast
10.6
GPT-5.1 (high)
7.8
GPT-5.2 (high)
7.1
K-EXAONE-236B-A23B
6.3

Avg Token Usage

K-EXAONE-236B-A23B
12,259
Kanana-2-30B-Thinking
9,114
Kanana-2-30B-Thinking-2601
6,664
Llama-VARCO-8B-Instruct
6,041
HCX-007(high)
5,122
Gemini-3-Pro-Preview
4,633
Solar-Pro-2 (31B)(high)
4,521
Solar-Open-100B
4,423
Grok-4.1-fast
4,352
A.X-4.0 (72B)
3,481
Claude-Opus-4.5
3,452
GPT-5.2 (high)
3,014
K-EXAONE-236B-A23B
2,962
Deepseek-V3.2
2,931
GPT-5.1 (high)
2,481
EXAONE-4.0.1-32B (high)
1,752