Respuesta :
Answer:
The 95% confidence interval for the average credit score is between 697.675 and 802.325
Step-by-step explanation:
We are in posession of the sample standard deviation, so the t-distribution is used to solve this question.
The first step to solve this problem is finding how many degrees of freedom, we have. This is the sample size subtracted by 1. So
df = 20 - 1 = 19
95% confidence interval
Now, we have to find a value of T, which is found looking at the t table, with 19 degrees of freedom(y-axis) and a confidence level of [tex]1 - \frac{1 - 0.95}{2} = 0.975[/tex]. So we have T = 2.093
The margin of error is:
M = T*s = 2.093*25 = 52.325
In which s is the standard deviation of the sample.
The lower end of the interval is the sample mean subtracted by M. So it is 750 - 52.325 = 697.675
The upper end of the interval is the sample mean added to M. So it is 750 - 52.325 = 802.325
The 95% confidence interval for the average credit score is between 697.675 and 802.325
