The average cost of an IRS Form 1040 tax filing at Thetis Tax Service is $138.00. Assuming a normal distribution, if 77 percent

Question

3 years ago

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The average cost of an IRS Form 1040 tax filing at Thetis Tax Service is $138.00. Assuming a normal distribution, if 77 percent

of the filings cost less than $155.00, what is the standard deviation? Hint: Use Excel or Appendix C-2 to find the z-score. (Round your answer to 2 decimal places.) Standard deviation $

Mathematics

1 answer:

jek_recluse [69] · Answer 1 · 2022-09-04T02:08:16+03:00

Answer:

22.97

Step-by-step explanation:

Given that the average cost of an IRS Form 1040 tax filing at Thetis Tax Service is $138.00.

Let x be the average cost an IRS Form 1040 tax filing at Thetis Tax Service

$P(X$ is given

From std normal distribution table we find 77th percentile z value.

z=0.74

Corresponding X value = 155

i.e. $0.74=\frac{155-138}{s}$ where s is the std deviation

Simplify to get

Std deviation = $\frac{17}{0.74} \\=22.97$