Answer:
(a) 0.0162
(b) 0.9838
(c) 0.4131
(d) 0.3969
Explanation:
To find the proportion of observations from a standard normal distribution that falls in each of the given regions, we can use Table A (also known as the standard normal distribution table or z-table).
(a) z ≤ -2.14:
To find the proportion of observations with z ≤ -2.14, we need to find the area under the standard normal curve to the left of -2.14.
From Table A, the value for -2.1 falls between the z-scores -2.13 and -2.14. The corresponding area in the table is 0.0162.
Therefore, the proportion of observations with z ≤ -2.14 is approximately 0.0162.
(b) z ≥ -2.14:
To find the proportion of observations with z ≥ -2.14, we need to find the area under the standard normal curve to the right of -2.14.
The area to the left of -2.14 is 0.0162 (as found in part (a)). We can subtract this value from 1 to get the area to the right.
1 - 0.0162 = 0.9838
Therefore, the proportion of observations with z ≥ -2.14 is approximately 0.9838.
(c) z > 1.37:
To find the proportion of observations with z > 1.37, we need to find the area under the standard normal curve to the right of 1.37.
From Table A, the value for 1.3 falls between the z-scores 1.36 and 1.37. The corresponding area in the table is 0.4131.
Therefore, the proportion of observations with z > 1.37 is approximately 0.4131.
(d) -2.14 < z < 1.37:
To find the proportion of observations with -2.14 < z < 1.37, we need to find the area under the standard normal curve between these two z-values.
The area to the left of -2.14 is 0.0162 (as found in part (a)). The area to the right of 1.37 is 0.4131 (as found in part (c)).
To find the area between these two values, we subtract the smaller area from the larger area:
0.4131 - 0.0162 = 0.3969
Therefore, the proportion of observations with -2.14 < z < 1.37 is approximately 0.3969.