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Question 9
The mean IQ score of a sample of 54 students selected from a high school is 89. Suppose the standard deviation of IQ's at this school is σ = 8.6. The 99% confidence interval for the population mean (rounded to two decimal places) is:
The lower limit is
The upper limit is
Question 2
A sample of size 118 from a population having standard deviation σ = 9 produced a mean of 42. The 99% confidence interval for the population mean (rounded to two decimal places) is:
The lower limit is
The upper limit is
Question 3The mean federal income tax paid last year by a random sample of 35 persons selected from a city was $4311. Suppose the standard deviation of tax paid in this city is σ = $898. The 95% confidence interval for the population mean (rounded to two decimal places) is:
The lower limit is $
The upper limit is $
Question 8A random sample of 96 customers, who visited a department store, spent an average of $75 at this store. Suppose the standard deviation of expenditures at this store is σ = $16. The 98% confidence interval for the population mean (rounded to two decimal places) is:
The lower limit is $
The upper limit is $
