Answer: 20 ± 11.32
Explanation: <u>Confidence</u> <u>Interval</u> (CI) is an interval of values where there is a % certainty the true mean value lies in. For example, a 95% CI means there is a 95% certainty the true mean value lies in the interval.
For the data set 2, z-value for 95% confidence interval is z = 1.96
Formula to calculate CI is
x ±
where
x is mean
z is z-value
s is standard deviation
n is the sample number
Then:
20 ±
20 ±
20 ±
20 ± 11.32
The 95% CI is 20 ± 11.32, which means there is a 95% certainty the true value is between 8.68 and 31.32.