In: Statistics and Probability
3 The ten most recent cars sold at a dealership have an average price of $24,525 with a standard deviation of s = $450. Assuming that the prices of all cars sold by the dealership have an approximately normal distribution, find the 98% confidence interval for the mean price of all cars sold by the dealership, to the nearest dollar.
Conclusion: We can be ___________confident that the mean price of all cars sold by the dealership is between $ ________________ and $ ___________________3
Solution :
Given that,
= $24525
s = $450
n = 10
Degrees of freedom = df = n - 1 = 10 - 1 = 9
At 98% confidence level the t is ,
= 1 - 98% = 1 - 0.98 = 0.02
/ 2 = 0.02 / 2 = 0.01
t /2,df = t0.01,9 =2.821
Margin of error = E = t/2,df * (s /n)
= 2.821 * (450 / 10) = 401
The 98% confidence interval estimate of the population mean is,
- E < < + E
24525 - 401 < < 24525 + 401
24124 < < 24926
(24124 , 24926 )
We can be _____98%______confident that the mean price of all cars sold by the dealership is between $24124 and $ 24926