Find the sample mean

Question

Research of selling prices for used two-year old Corvettes reveals th at they have a standard deviation of $2517. How many selling prices you must obtain in order to estimates the mean selling price of these cars? Assume you want 98% CI that your sample mean is within $250 of the population mean. It is likely that you will find that many two-year-old used Corvettes in your region?

Answer 1

Step 1:

The standard deviation of selling prices for used two-year old Corvettes σ is $ 2517.

98 % confidence interval of sample mean is within $ 250.

Here margin of error E is 250.

Z for 98 % confidence interval is 2.33.

Margin of error : ,

where Z is the Z-score for 98 % of confidence interval.

σ is the standard deviation

n is sample size.

Step 2:

Find the population mean .

Sample size of the selling prices for used two-year old Corvettes is 550.

Solution:

Sample size of the selling prices for used two-year old Corvettes is 550.

Answer 2

Step 1:

The standard deviation of selling prices for used two-year old Corvettes σ is $ 2517.

98 % confidence interval of sample mean is within $ 250.

Here margin of error E is 250.

Calculate the z score for 98 % confidence using Ti -84 calculator.

Follow these steps to evaluate z score for top 98 % confidence.

1.Select invNorm() in Ti -84 calculator.

[ 2nd --> VARS --> 3 ]

2.Enter area in decimals .

invNorm((1 - 0.98)/2)

invNorm(0.01)

3.Now press Enter in calculator to view answer

invNorm(0.01) = - 2.33.

|Z | score for 98 % confidence interval is 2.33.

Margin of error : ,

where Z is the Z-score for 98 % of confidence interval.

σ is the standard deviation

n is sample size.

Step 2:

Find the population mean .

Sample size of the selling prices for used two-year old Corvettes is 550.

Solution:

Sample size of the selling prices for used two-year old Corvettes is 550.