Question

One of the characteristics of a credit card is the average outstanding balance. A group of researchers wants to estimate the average outstanding balance using a randomly selected sample of 60 customers. The average monthly balance of the sample is calculated as $1531.43. Construct and interpret a 90% confidence interval for the average outstanding balance assuming that the population standard deviation is $2514.

1. Procedure: Select an answer One proportion Z procedure One mean T procedure One variance χ² procedure One mean Z procedure  
2. Assumptions: (select everything that applies)
   • Simple random sample
   • Normal population
   • Sample size is greater than 30
   • The number of positive and negative responses are both greater than 10
   • Population standard deviation is known
   • Population standard deviation is unknown
3. Unknown parameter: Select an answer σ², population variance μ, population mean p, population proportion  
4. Point estimate: Select an answer sample proportion, p̂ sample variance, s² sample mean, x̄  =dollars (Round the answer to 2 decimal places)
5. Confidence level % and α=α= , also
   • α2=α2= , and 1−α2=1-α2=
   • Critical values: (Round the answer to 2 decimal places)
     • left= right=
6. Margin of error (if applicable):  (Round the answer to 2 decimal places)
7. Lower bound:  (Round the answer to 2 decimal places)
8. Upper bound:  (Round the answer to 2 decimal places)
9. Confidence interval:(, )
10. Interpretation: We are % confident that the average outstanding balance on a credit card is between dollars and dollars.

Answer 1