Math Problem Statement

A factory that manufactures bolts is performing a quality control experiment. Each object should have a length of no more than 16 centimeters. The factory believes that the length of the bolts exceeds this value and measures the length of 69 bolts. The sample mean bolt length was 16.03 centimeters. The population standard deviation is known to be σ=0.24 centimeters. What is the test statistic z?

What is the p-value?

Does sufficient evidence exist that the length of bolts is actually greater than the mean value at a significance level of α=0.01?

Solution

To solve this problem, we need to determine:

  1. The test statistic zz: The formula for zz-score is: z=xˉμσ/nz = \frac{\bar{x} - \mu}{\sigma / \sqrt{n}} where:

    • xˉ=16.03\bar{x} = 16.03 (sample mean),
    • μ=16\mu = 16 (hypothesized population mean),
    • σ=0.24\sigma = 0.24 (population standard deviation),
    • n=69n = 69 (sample size).

    Substituting the values: z=16.03160.24/69z = \frac{16.03 - 16}{0.24 / \sqrt{69}}

  2. The p-value: Since this is a one-tailed test (testing whether the mean is greater than 16), the p-value is the area to the right of the calculated zz-score under the standard normal curve.

  3. Decision based on significance level α=0.01\alpha = 0.01: We compare the pp-value to α\alpha. If p<αp < \alpha, we reject the null hypothesis H0:μ=16H_0: \mu = 16.

Let me calculate these values.import scipy.stats as stats import math

Given data

x_bar = 16.03 # sample mean mu = 16 # hypothesized population mean sigma = 0.24 # population standard deviation n = 69 # sample size alpha = 0.01 # significance level

Calculate the test statistic z

z = (x_bar - mu) / (sigma / math.sqrt(n))

Calculate the p-value for a one-tailed test

p_value = 1 - stats.norm.cdf(z)

z, p_value(1.0383279828647987, 0.14955869261591692)(1.0383279828647987, 0.14955869261591692)success1. Test statistic zz: 1.0381.038
2. p-value: 0.1500.150

Decision:

Since the pp-value (0.1500.150) is greater than the significance level α=0.01\alpha = 0.01, there is not sufficient evidence to conclude that the mean length of the bolts is greater than 16 centimeters. The null hypothesis cannot be rejected.


Do you have any further questions or need detailed steps? Here are 5 related questions to explore:

  1. How is the zz-score affected by changes in sample size?
  2. What is the relationship between the pp-value and the level of significance α\alpha?
  3. Can this test be performed with a smaller sample size and still maintain validity?
  4. What would the conclusion be if the significance level were α=0.05\alpha = 0.05?
  5. How does the population standard deviation influence the outcome of the test?

Tip: Always double-check the direction of the hypothesis (one-tailed or two-tailed) when determining the pp-value.

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Math Problem Analysis

Mathematical Concepts

Statistics
Hypothesis Testing
Z-Score Calculation
Significance Testing

Formulas

z = (x̄ - μ) / (σ / √n)
p-value for one-tailed test = 1 - Φ(z)

Theorems

Central Limit Theorem
Properties of the Standard Normal Distribution

Suitable Grade Level

Undergraduate (Introductory Statistics)