Math119Sols4S11

# Math119Sols4S11 - QUIZ 4(CHAPTER 7 SOLUTIONS MATH 119...

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QUIZ 4 (CHAPTER 7) SOLUTIONS MATH 119 – SPRING 2011 – KUNIYUKI 105 POINTS TOTAL, BUT 100 POINTS = 100% Do not leave “+”, “ ± ”, or ± ” in your final confidence intervals; write the lower limit and the upper limit of each interval, as we have done in class. Avoid rounding until you write the simplified margin of error or your final answer. Then, round to the same number of decimal places as the given value of x , s , or s 2 . If you want to round in the middle of a problem, round to at least five significant digits. (We're assuming that the population of interest is much larger than the sample, so there is no need to use a finite population correction factor. Do not use continuity corrections.) 1) We will conduct a survey to estimate the average number of gifts purchased by American families the day after Thanksgiving. We want to have 92% confidence that the resulting sample mean will be within 0.3 gifts of the true population mean. Assuming that the population standard deviation is 3.7 gifts (based on a similar survey conducted last year), how many families should be in the sample? Use the formula: n = z ± /2 ² E ³ ´ µ · ¸ 2 ¹ º º º » ¼ ¼ ¼ (8 points) Find the critical values (CVs) for a 92% confidence interval. The negative CV is about ± 1.75 (actually, it is between ± 1.75 and ± 1.76). Therefore, the positive CV, z , is about 1.75. (Note that 1.76 would be the more conservative choice.) n = 1.75 () 3.7 0.3 ± ² ³ ´ µ 2 · ¸ ¸ ¸ ¸ ¹ º º º º , or, conservatively, = 466 families · » ¹ ¼ n = 1.76 3.7 0.3 ± ² ³ ´ µ 2 · ¸ ¸ ¸ ¸ ¹ º º º º = 472 families · » ¹ ¼

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2) The Barry Bonds Exercise Company is testing a new piece of exercise equipment in its standard mode. The company wants to know about the lengths of time that adult American males can endure on the equipment. Assume that
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Math119Sols4S11 - QUIZ 4(CHAPTER 7 SOLUTIONS MATH 119...

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