In: Statistics and Probability
Scholastic Aptitude Test (SAT) mathematics scores of a random sample of 100 high school seniors in the state of Texas are collected, and the sample mean and standard deviation are found to be 520 and 80, respectively. Find a 95% confidence interval on the mean SAT mathematics score for seniors in the state of Texas.
= Solution :
Given that,
sample mean =
= 520
Population standard deviation =
= 80
Sample size n =100
At 95% confidence level the z is ,
= 1 - 95% = 1 - 0.95 = 0.05
/ 2 = 0.05 / 2 = 0.025
Z/2 = Z0.025 = 1.96 ( Using z table )
Margin of error = E = Z/2
* (
/n)
= 1.96* ( 80 / 100
)
= 15.68
At 95% confidence interval IS
- E <
<
+ E
520 - 15.68 < <520 + 15.68
(504.32 , 535.68)