Question

Ten people at a party decide to compare ages. Five people are 30 years old, three are 32, one is 31, and one is 65.

Answer 1

Given:
Ten People
5 people = 30 years old
3 people = 32 years old
1 person = 31 years old
1 person = 65 years old

We need to arrange the ages in order from least to greatest.

30, 30, 30, 30, 30, 31, 32, 32, 32, 65 
65 is the outlier. 

A.) mean age without the outlier. count of the numbers : 9
5 x 30 =    150
1 x 31 =      31
3 x 32 =      96
total age  277
÷ # of pax    9
mean         30.77 round to the nearest tenth 30.80

b.) Standard deviation:
We need to calculate variance first:
5 pax : 30 - 30.80 = - 0.80 ⇒ -0.80² = 0.64 * 5pax = 3.20
1 pax : 31 - 30.80 =   0.20 ⇒  0.20²  = 0.04 * 1pax = 0.04
3 pax : 32 - 30.80 =   1.20 ⇒  1.20² = 1.44 * 3 pax = 4.32

Variance : (3.20 + 0.04 + 4.32) / 9 pax = 7.56 / 9 = 0.84

Standard deviation is simply the square root of the variance.

Standard deviation = √0.84 = 0.916 

0.916 round to nearest hundredths is 0.92
0.916 round to nearest tenths is 0.90