5.3. Connecting the Standard Deviation and Normal Distribution http://www.ck12.org
(b) 95% of students= 0. 95 ×325 students=308 students
Therefore 308 students studied between 2.2 and 7 hours.
(c)
1
2( 99 .7%−68%) =
1
2
( 31 .7%)
= 15 .85%
15.85 % of the students studied longer than 5.8 hours.
(d) Harry is not a typical student. The mean is 4.6 hours; therefore the majority of students studied more than 4
hours more than Harry did for the exam. Harry is lucky to have received a 60% on the exam.
- (a)
(b) Almost all dogs have a life span of 7 years 11 months to 12 years 5 months.
(c)
34%+34%=68%
( 0. 68 × 825 = 561 )In a sample of 825 dogs, 561 would have a life expectancy between 9 years 5 months to 10 years 11 months.
(d)
13 .5%+ 2 .35%= 15 .85%
0. 1585 × 825 = 130. 76In a sample of 825 dogs, 130 would have a life expectancy of more than 10 years 11 months.
TABLE5.6:
Datax Mean(x ̄) (Data –Mean)(x−x ̄) (Data - Mean)^2 (x−x ̄)^2
8 9.5 -1.5 2.25
8 9.5 -1.5 2.25
9 9.5 -0.5 0.25
9 9.5 -0.5 0.25
9 9.5 -0.5 0.25
9.5 9.5 0 0
9.5 9.5 0 0