Page 181 - Probability Demystified

170 CHAPTER 9 The Normal Distribution

Fig. 9-19.

The area for z ¼ 1.3 is 0.903. Since we are looking for an area less
than z ¼ 1.3, use the value found in the table. Hence the probability
that the city receives less than 53 inches of snow is 0.903 or 90.3%.

108 120 12
4. z ¼ ¼ ¼ 1:2
10 10

The required area is shown in Figure 9-20.

Fig. 9-20.

The area for z ¼ 1.2 is 0.115. Since we are looking for the area less
than z ¼ 1.2, use the value in the table. Hence the probability that a
person has a systolic blood pressure less than 108 is 0.115 or 11.5%.

2:8 2:5 0:3
5. z ¼ ¼ ¼ 0:6
0:5 0:5
2:2 2:5 0:3
z ¼ ¼ ¼ 0:6
0:5 0:5
The required area is shown in Figure 9-21.