Hi
using the Data Analysis Tool in Excel
by Entering data into column:15,19,17,23,21,17,16,18,12,18,20,22,15,18,20
and choosing statistical analysis
a. Mean 271/15 = 18.0667
b. Variance = 8.4952
c. Standard deviation = sqrt(8.4952) = 2.9147
Recommend using methods at Your disposable to check these responses.