Math Problem Statement

Police sometimes measure shoe prints at crime scenes so that they can learn something about criminals. Listed below are shoe print lengths, foot lengths, and heights of males. Construct a scatterplot, find the value of the linear correlation coefficient r, and find the P-value of r. Determine whether there is sufficient evidence to support a claim of linear correlation between the two variables. Based on these results, does it appear that police can use a shoe print length to estimate the height of a male? Use a significance level of α = 0.05.

Solution

To solve this problem, we need to address several steps systematically:

  1. Scatterplot Construction: The data provided involves shoe print lengths (cm) and heights (cm). Based on the scatterplot choices, the points plotted must align with the given data. By inspecting the scatterplots provided, the correct choice appears to be B, where the data points match the given values.

  2. Linear Correlation Coefficient (r): The correlation coefficient, rr, measures the strength and direction of the linear relationship between two variables. To compute rr: r=((xxˉ)(yyˉ))(xxˉ)2(yyˉ)2r = \frac{\sum \left( (x - \bar{x})(y - \bar{y}) \right)}{\sqrt{\sum (x - \bar{x})^2 \sum (y - \bar{y})^2}} Here, xx represents the shoe print length and yy represents height. We will calculate this using the data provided.

  3. P-Value and Significance Test: Once rr is calculated, we determine whether the linear correlation is significant using the t-test: t=rn21r2t = r \sqrt{\frac{n - 2}{1 - r^2}} The p-value is obtained using the degrees of freedom df=n2df = n - 2, where nn is the number of data pairs.

  4. Analysis and Conclusion: If the p-value is less than the significance level (α=0.05\alpha = 0.05), we conclude that there is sufficient evidence to support the claim that shoe print length can be used to estimate height.

Let me calculate these values for you from scipy.stats import t

Data from the table

shoe_print = np.array([30.5, 30.5, 30.4, 30.7, 26.9]) height = np.array([176.9, 184.2, 181.9, 179.2, 177.3])

Calculate means

mean_shoe_print = np.mean(shoe_print) mean_height = np.mean(height)

Calculate the numerator and denominator for r

numerator = np.sum((shoe_print - mean_shoe_print) * (height - mean_height)) denominator = np.sqrt(np.sum((shoe_print - mean_shoe_print)**2) * np.sum((height - mean_height)**2)) r = numerator / denominator

Degrees of freedom

n = len(shoe_print) df = n - 2

Calculate t-statistic

t_statistic = r * np.sqrt((n - 2) / (1 - r**2))

Calculate p-value (two-tailed)

p_value = 2 * t.sf(abs(t_statistic), df)

r, pThe linear correlation coefficient rr is approximately 0.446, indicating a moderate positive correlation between shoe print length and height.

The p-value is approximately 0.452, which is greater than the significance level (α=0.05\alpha = 0.05).

Conclusion:

There is insufficient evidence to support the claim of a significant linear correlation between shoe print length and height at the 0.05 significance level.

Would you like further details or explanations? Here are some related questions for further exploration:

  1. How is the correlation coefficient rr computed step-by-step?
  2. What does a p-value greater than α\alpha indicate in hypothesis testing?
  3. Could using a larger dataset improve the reliability of this analysis?
  4. How does the t-distribution play a role in calculating the p-value?
  5. What other statistical methods could we use to estimate height from shoe print data?

Tip: Ensure the sample size is sufficiently large to

Ask a new question for Free

By Image

Drop file here or Click Here to upload

Math Problem Analysis

Mathematical Concepts

Linear correlation
Scatterplot construction
Hypothesis testing
Significance testing

Formulas

r = Σ((x - x̄)(y - ȳ)) / √(Σ(x - x̄)² * Σ(y - ȳ)²)
t = r * √((n - 2) / (1 - r²))
P-value calculation based on t-distribution

Theorems

Pearson's correlation coefficient
t-distribution for significance testing

Suitable Grade Level

Undergraduate (Statistics 101 or Data Analysis)