Respuesta :
Answer:
A 95% confidence interval estimate of the population mean (average) daily balance of all the checking accounts is $274.32 to $331.68
Step-by-step explanation:
Consider the provided information.
A random sample of 21 checking accounts at the bank are chosen,
That means n=21
df = n-1
df = 21-1=20
We need to Construct and interpret a 95% confidence interval.
Determine t critical value for 95% confidence interval.
0.95=1-α
α=0.05
The sample size is small and it is a two tailed test.
From the t value table confidence interval is 2.086
An average daily balance is $303 and a standard deviation of $63.
[tex]CI=\bar x\pm t_c \times \frac{s}{\sqrt{n}}[/tex]
Substitute the respective values.
[tex]CI=303\pm 2.086 \times \frac{63}{\sqrt{21}}[/tex]
[tex]CI=303\pm 28.68[/tex]
[tex]CI=274.32\ or\ 331.68[/tex]
A 95% confidence interval estimate of the population mean (average) daily balance of all the checking accounts is $274.32 to $331.68
