http://www.ck12.org Chapter 5. The Shape, Center and Spread of a Normal Distribution - Basic
- A group of physically active women were asked to record the number of hours they spent at the gym each
week. The results are shown below.
8 8 9 9 9 9. 5 9. 5 9. 5 9. 5 9. 5
9. 5 9. 5 9. 5 9. 5 9. 5 10 10 10 11 11
Calculate the standard deviation.- A normal distribution curve shows a mean(x ̄)and a standard deviation(σ). Approximately what percentage
of the data would lie in the intervals with the limits shown?
a. ̄x− 2 σ,x ̄+ 2 σ
b. ̄x,x ̄+ 2 σ
c. ̄x−σ,x ̄+σ
d. ̄x−σ,x ̄
e. ̄x−σ,x ̄+ 2 σ- Use the 68-95-99.7 rule on a normal distribution of data with a mean of 185 and a standard deviation of 10, to
answer the following questions. What percentage of the data would measure
a. between 175 and 195?
b. between 195 and 205?
c. between 155 and 215?
d. between 165 and 185?
e. between 185 and 215?Review Answers
- 1.σ^2 = 33 σ= 5. 74
2.σ^2 = 35. 24 σ= 5. 94
3.σ^2 = 111. 28 σ= 10. 55
4.σ^2 = 64. 96 σ= 8. 06
2.
(b) 68% of the plants have a height between 11.15 cm and 11.65 cm.
0. 68 (x) = 225x=225
0. 68
x= 331Therefore there were 331 strawberry plants in the greenhouse.