Math Problem Statement

An insurance company wants to know if the color of an automobile has a relationship with the number of moving violations. The following contingency table gives the results of data collected from police reports across the nation. The columns list the numbers of reported moving violations in a year. Use a level of significance of α=0.01 to conduct a hypothesis test of association between automobile color and the number of moving violations.

Observed Sample of Cars 0 -1 2 -3 More Than 3 Total White 64 65 26 155 Black 56 21 13 90 Red 77 47 28 152 Silver 61 43 17 121 Other 44 25 6 75 Total 302 201 90 593

Step 1 of 4 : Calculate the expected value for the number of white cars with 0 -1 moving violations in a year. Round your answer to six decimal places.

Solution

To calculate the expected value for the number of white cars with 0-1 moving violations in a year, we can use the formula for expected frequency in a contingency table:

Eij=(RowTotal)×(ColumnTotal)GrandTotalE_{ij} = \frac{(Row \, Total) \times (Column \, Total)}{Grand \, Total}

Where:

  • EijE_{ij} is the expected frequency for the cell corresponding to row ii and column jj.
  • RowTotalRow \, Total is the total number of cars in the particular row (for white cars in this case).
  • ColumnTotalColumn \, Total is the total number of cars in the particular column (for 0-1 moving violations in this case).
  • GrandTotalGrand \, Total is the total number of observations.

From the contingency table:

  • Row Total for white cars: 64+65+26+155=31064 + 65 + 26 + 155 = 310
  • Column Total for 0-1 moving violations: 64+56+77+61+44=30264 + 56 + 77 + 61 + 44 = 302
  • Grand Total: 593593

Now, using the formula to find the expected value for the number of white cars with 0-1 moving violations:

Ewhite, 0-1=(310)×(302)593E_{\text{white, 0-1}} = \frac{(310) \times (302)}{593}

Let's calculate this:

Ewhite, 0-1=93620593157.974115E_{\text{white, 0-1}} = \frac{93620}{593} \approx 157.974115

Thus, the expected value for the number of white cars with 0-1 moving violations is approximately 157.974115.

Would you like to proceed with the next step or need further clarification?

Related Questions:

  1. How do we calculate the expected values for all the other cells in the table?
  2. What is the next step in the hypothesis testing procedure after calculating the expected values?
  3. What is the formula for the chi-square statistic in this case?
  4. How do we interpret the results of a chi-square test?
  5. Why is a significance level of 0.01 used in this test?

Tip:

When performing chi-square tests, always ensure that your expected values are sufficiently large (typically at least 5). If many cells have expected values less than 5, the test may not be reliable.

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Math Problem Analysis

Mathematical Concepts

Chi-Square Test
Contingency Table
Expected Frequency

Formulas

E_{ij} = (Row Total × Column Total) / Grand Total

Theorems

Chi-Square Test of Independence

Suitable Grade Level

Grades 11-12