In: Statistics and Probability
In a random sample of 100 audited estate tax returns, it was determined that the mean amount of additional tax owed was $3494 with a standard deviation of $2527. Construct and interpret a 90% confidence interval for the mean additional amount of tax owed for estate tax returns.
( , )
Solution :
Given that,
Point estimate = sample mean = = 3494
Population standard deviation =
= 2527
Sample size = n =100
At 90% confidence level the z is
= 1 - 90% = 1 - 0.90 = 0.1
/ 2 = 0.1 / 2 = 0.05
Z/2 = Z0.05 = 1.645 ( Using z table )
Margin of error = E = Z/2
* (
/n)
= 1.645 * (2527 / 100
)
= 415.7
At 90% confidence interval
is,
- E < < + E
3494 - 415.7 <
< 3494+ 415.7
3078.3 <
< 3909.7