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On Tuesday, an insurance company receives a total of 10 claims for automobile policies. After the first-round assessment, it's found that the mean claim amount of the 10 claims is $426 while the standard deviation is 112. On Tuesday, the chief claims analyst authorizes the removal of one of the claims for $545 from the list on grounds that it's fraught with fraud. Compute the standard deviation for the remaining set of 9 claims.
A
110.2
B
12145.2
C
421.8
D
420
Explanation:
Step-by-step solution:
Calculate total sum of original 10 claims: Σx = mean × n = 426 × 10 = 4,260
Calculate total sum after removing fraudulent claim: New Σx = 4,260 - 545 = 3,715
Calculate new mean for 9 claims: New mean = 3,715 ÷ 9 = 412.777... ≈ 412.8
Calculate sum of squares for original 10 claims: Using formula: s² = 1/(n-1)[Σx² - nẍ²] 112² = 1/9[Σx² - 10 × 426²] 12,544 = 1/9[Σx² - 1,814,760] Σx² = 12,544 × 9 + 1,814,760 = 112,896 + 1,814,760 = 1,927,656
Calculate sum of squares after removing fraudulent claim: New Σx² = 1,927,656 - 545² = 1,927,656 - 297,025 = 1,630,631
Calculate variance for remaining 9 claims: s² = 1/(9-1)[1,630,631 - 9 × 412.8²] s² = 1/8[1,630,631 - 9 × 170,403.84] s² = 1/8[1,630,631 - 1,533,634.56] s² = 1/8[96,996.44] = 12,124.555
Calculate standard deviation: s = √12,124.555 = 110.2
Key formulas used:
Note: The slight difference in variance calculation (12,145.2 vs 12,124.555) is due to rounding of the mean to 412.8. Using the exact mean of 412.777... gives the exact variance of 12,145.2 as shown in the original solution.