The lower bound of this interval is The upper bound of this

The lower bound of this interval is?

The upper bound of this interval is?

Solution

Confidence Interval
CI = x ± t a/2 * (sd/ Sqrt(n))
Where,
x = Mean
sd = Standard Deviation
a = 1 - (Confidence Level/100)
ta/2 = t-table value
CI = Confidence Interval
Mean(x)=19
Standard deviation( sd )=3.5
Sample Size(n)=64
Confidence Interval = [ 19 ± t a/2 ( 3.5/ Sqrt ( 64) ) ]
= [ 19 - 1.669 * (0.438) , 19 + 1.669 * (0.438) ]
= [ 18.27,19.73 ]