TRY IT YOURSELF ANSWERS A39 7. x P(x) 0 0.284 1 0.420 2 0.233 3 0.057 4 0.005 Adults Probability 0.1 0.2 0.3 0.4 0.5 0 1 2 3 4 Adults Who Have Not Read a Book in the Past Year P(x) x 8. m ≈ 13.6; s 2 ≈ 7.6; s ≈ 2.8; On average, there are about 14 clear days during the month of May. A May with fewer than 8 clear days or more than 19 clear days would be unusual. Section 4.3 1. 0.066 2. 0.185 3. 0.0002 Chapter 5 Section 5.1 1. (1) Curve B has the greatest mean. (2) Curve C is more spread out, so curve C has the greatest standard deviation. 2. m = 18; s = 5.8 3. (1) 0.0143 (2) 0.9850 4. 0.9834 5. 0.9846 6. 0.0733 Section 5.2 1. 0.1957 2. 0.7357; 147 3. 0.214 Section 5.3 1. (1) -1.77 (2) 1.96 2. (1) -1.28 (2) -0.84 (3) 2.33 3. (1) 17.05 pounds (2) 97 pounds (3) 60.7 pounds 17.05 pounds is to the left of the mean, 97 pounds is to the right of the mean, and 60.7 pounds is to the right of the mean. 4. The longest braking distance one of these cars could have and still be in the bottom 1% is about 120 feet. 5. The maximum length of time an employee could have worked and still be laid off is about 8.5 years. Section 5.4 1. Sample Mean 1, 1, 1 1 1, 1, 3 1.67 1, 1, 5 2.33 1, 3, 1 1.67 1, 3, 3 2.33 1, 3, 5 3 1, 5, 1 2.33 1, 5, 3 3 1, 5, 5 3.67 3, 1, 1 1.67 3, 1, 3 2.33 3, 1, 5 3 3, 3, 1 2.33 3, 3, 3 3 Sample Mean 3, 3, 5 3.67 3, 5, 1 3 3, 5, 3 3.67 3, 5, 5 4.33 5, 1, 1 2.33 5, 1, 3 3 5, 1, 5 3.67 5, 3, 1 3 5, 3, 3 3.67 5, 3, 5 4.33 5, 5, 1 3.67 5, 5, 3 4.33 5, 5, 5 5 mx = 3; 1sx2 2 ≈ 0.889; sx ≈ 0.943 mx = m = 3 1sx2 2 = s 2 n = 8 3 3 = 8 9 ≈ 0.889 sx = s2 n = 28 3 23 = 28 3 ≈ 0.943 2. mx = 6.9; sx = 0.1875 n = 64 n = 100 x Mean of sleep times (in hours) 6.5 6.7 6.9 7.1 7.3 With a smaller sample size, the mean stays the same but the standard deviation increases. 3. mx = 3.5, sx = 0.05 3.50 3.55 3.65 3.35 3.40 3.45 3.60 x Mean diameter (in feet) 4. 0.8324 5. 0.9332 (Tech: 0.9336) 6. 0.4702; 0.4065 There is about a 47% chance that a monitor will cost less than $200. There is about a 41% chance that the mean of a sample of 10 monitors is less than $200. Section 5.5 1. Because np and nq are greater than 5, a normal distribution can be used. 2. (1) 56.5 6 x 6 83.5 (2) x 6 54.5 3. 0.8264 (Tech: 0.8273) 4. 0.0281 5. 0.0479 (Tech: 0.0476)
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