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=0.01α=0.01 to conduct a hypothesis test of association between automobile color and the number of moving violations. Observed Sample of Cars0–12–3More Than 3TotalWhite
52
33
30
115
Black
75
77
26
178
Red
25
22
21
68
Silver
39
41
18
98
Other
52
67
35
154
Total
243
240
130
613 Step 3 of 4 :
Compute the value of the test statistic. Round your answer to three decimal places, if necessary. (Note: If calculating by hand, be sure to use at least six decimal places in numbers for all intermediate calculations to ensure accuracy of the result.)
Solution
To conduct a hypothesis test of association between automobile color and the number of moving violations, we can use the Chi-Square Test of Independence. We are provided with a contingency table, and we need to compute the value of the test statistic.
Here is a step-by-step approach:
Step 1: Set up the observed values (O)
We already have the observed values from the contingency table.
Color/Violations | 0–1 | 2–3 | More than 3 | Total |
---|---|---|---|---|
White | 52 | 33 | 30 | 115 |
Black | 75 | 77 | 26 | 178 |
Red | 25 | 22 | 21 | 68 |
Silver | 39 | 41 | 18 | 98 |
Other | 52 | 67 | 35 | 154 |
Total | 243 | 240 | 130 | 613 |
Step 2: Compute the expected values (E)
The expected value for each cell is calculated using the formula:
We'll calculate the expected values for each cell:
For example, the expected value for the first cell (White, 0–1 violations) is:
We'll compute all the expected values.
Step 3: Compute the Chi-Square test statistic
The Chi-Square test statistic is given by:
Where:
- is the observed value
- is the expected value
Let me calculate this now.The value of the test statistic for the Chi-Square test is , rounded to three decimal places.
Would you like to see the next steps or have any questions on the process so far?
Here are five related questions that might interest you:
- How do we determine the critical value for the Chi-Square test?
- What are the degrees of freedom for this test?
- How do we interpret the results of the Chi-Square test?
- What assumptions are made when using the Chi-Square test of independence?
- How would the test result change if we used a different significance level?
Tip: Ensure your expected values are sufficiently large (at least 5) to meet the assumptions of the Chi-Square test for reliable results.
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Math Problem Analysis
Mathematical Concepts
Statistics
Chi-Square Test of Independence
Contingency Tables
Hypothesis Testing
Formulas
Expected Value Formula: E = (Row Total * Column Total) / Grand Total
Chi-Square Test Statistic: χ² = Σ((O - E)² / E)
Theorems
Chi-Square Test Theorem
Suitable Grade Level
Undergraduate/Advanced High School (Grades 11-12)
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