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Find the area under the standard normal curve a. between \(z=0\) and \(z=1.95\) b. between \(z=0\) and \(z=-2.05\) c. between \(z=1.15\) and \(z=2.37\) d. from \(z=-1.53\) to \(z=-2.88\) e. from \(z=-1.67\) to \(z=2.24\)

Short Answer

Expert verified
a) 0.4744 b) 0.4798 c) 0.1162 d) 0.0609 e) 0.9400

Step by step solution

01

Understanding Z-values

Z-values are standard deviations. A positive Z-score tells us how far to the right of the mean our point is, while a negative Z-score tells us how far to the left our point is.
02

Find Area using Z-table (a) between \(z=0\) and \(z=1.95\)

Look up the z-value in the z-table to find the area to the left of that z-value. The z-table gives us 0.9744 (this is to the left of the z-value). Since we want the area from the mean (z=0), we subtract 0.5 (area to the left of z=0) from our looked up area. So, 0.9744 - 0.5 = 0.4744.
03

Find Area using Z-table (b) between \(z=0\) and \(z=-2.05\)

Look up the absolute of z-value (2.05) in the z-table. We get 0.9798, which represents the area to the left. We want the area to the right of -2.05, so we do 1 - 0.9798 = 0.0202. We also subtract this from 0.5 (as we want area from mean), to get 0.5 - 0.0202 = 0.4798.
04

Find Area using Z-table (c) between \(z=1.15\) and \(z=2.37\)

Look up area to left for z=2.37 and z=1.15 in the z-table. We get 0.9911 and 0.8749 respectively. Subtract area corresponding to 1.15 from the area corresponding to 2.37. So, 0.9911 - 0.8749 = 0.1162.
05

Find Area using Z-table (d) from \(z=-1.53\) to \(z=-2.88\)

Look up area to left for absolute z-value of -1.53 and -2.88 in the z-table. We get 0.9370 and 0.9979 respectively. But, we need the areas to the right, so do 1 - 0.9370 = 0.0630 and 1 - 0.9979 = 0.0021.These are the areas to the right of -1.53 and -2.88 respectively. Now subtract area corresponding to 0.0021 from the area corresponding to 0.0630. So, 0.0630 - 0.0021 = 0.0609.
06

Find Area using Z-table (e) from \(z=-1.67\) to \(z=2.24\)

This comprises two parts; the area to the right of -1.67 and the area to the left of 2.24. Look up these two z-values in the z-table to get 0.9525 and 0.9875 respectively. Subtract area to the right of -1.67 from area to the left of 2.24; 0.9875 - (1 - 0.9525) = 0.9400.

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