A researcher claims that felons convicted of tax fraud spend less than 12 months in jail, on average. She takes a random sample of 18 such cases from court files and finds that the mean is 10.4 months with a standard deviation of 3.7 months. Test the claim using a level of significance of 10%. You may assume that the amount of time served by these felons is normally distributed. What evidence justifies the use of this test? Check all that apply:

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A researcher claims that felons convicted of tax fraud spend less than 12 months in jail, on average. She takes a random sample of 18 such cases from court files and finds that the mean is 10.4 months with a standard deviation of 3.7 months. Test the claim using a level of significance of 10%. You may assume that the amount of time served by these felons is normally distributed.

What evidence justifies the use of this test? Check all that apply:

  • There are two different samples being compared
  • np>5 and nq>5
  •  
  • The original population is approximately normal
  • The population standard deviation is not known
  • The population standard deviation is known
  • The sample size is larger than 30
  • The sample standard deviation is not known
Expert Solution
Step 1

Given,

Sample mean x=10.4Sample standard deviation(s)=3.7sample size (n)=18 Level of significanceα=0.10

The hypothesis to be tested here is-

H0:μ=12H1:μ<12

This is a left tailed test

The test statistics used for testing this hypothesis is "One-sample t-test". This is because-

  • The original population is assumed to be approximately normal.
  • Population standard deviation is not known.

The required test-statistics is obtained as-

t=x-μsn=10.4-123.718=-1.8347

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