Page 180 - Probability Demystified

CHAPTER 9 The Normal Distribution 169

Fig. 9-17.

290 300 10
2. z ¼ ¼ ¼ 0:5
20 20

260 300 40
z ¼ ¼ ¼ 2
20 20
The required area is shown in Figure 9-18.

Fig. 9-18.

The area for 0.5 is 0.309. The area for 2 is 0.023. Since we are
looking for the area between z ¼ 0.5 and z ¼ 2, subtract the areas.
Hence the probability that a person burns between 260 and 290
calories is 0.309 0.023 ¼ 0.286 or 28.6%.
53 40 13
3. z ¼ ¼ ¼ 1:3
10 10
The required area is shown in Figure 9-19.