Determining confidence interval for population variance

Reference no: EM1323018

Q1) Investment banker would like to evaluate percentage of new clients who will make certain type of investment. If she wishes a sampling error of new greater than 2.5% and confidence level of 90%, how many clients must she sample? What sample size is needed for 85% confidence level?

Q2) A manufacturer bonds plastic coating in metal surface. Random sample of nine observations n the thickness of this coating is taken from a week's output, and thickness in millimetres are as follows:

19.8 21.2 18.6 20.4 21.6 19.8 19.9 20.3 20.8

Suppose normality, determine a 90% confidence interval for population variance.

Q3) Large population of overdue bills has balances which follow a normal curve .When we take a sample of 100 of these average $500 and the SD is$100.

What statement can you make about range $300 to $700

What statement can you make about range $480 to $520

Reference no: EM1323018

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