Practice Items on the Normal Distribution

Statistics and Society 9/29/99 4 Scores on a statistics test were approximately Practice Items on the Normal Distribution normally distributed with mean 70 and standard deviation 10. The instructor wants to give A's to the top 1 Scores on a commonly used IQ test are approximately 16 percent of the class. Use the 68/95 rule to determine normally distributed with mean 100 and standard which scores should get A's? deviation 15. In a group of 1000 people, about how a) 70 and up b) 75 and up c) 80 and up many would have IQ's above 115? d) 84 and up e) 90 and up a) about 5 b) about 25 c) about 50 5 Which of the following should not be used with highly d) about 160 e) some other number skewed data? 2 Here are two stemplots. What statistics are the most a) the 68/95 rule b) a five number summary appropriate (valid, not misleading) descriptive statistics c) a stem plot d) the median for the 'typical' members of the distributions represented e) both a) and d) by these stemplots? 6 Diastolic blood pressure readings for a sample of 200 Stemplot I Stemplot II men are approximately normally distributed with mean 70. One hundred and thirty-six (136) of the men had 0 000000111112222333344 0 3 readings between 55 and 85. Use the 68/95 rule to 0 5567789 0 778 1 024 1 111233 decide which of the following is closest to the standard 1 7 1 555677799 deviation of the blood pressure readings. 2 2 000113344444 2 2 55566777788999 a) 1 b) 15 c) 30 d) 45 e) 90 3 2 3 00000111222 3 3 555667 4 1 4 000 7 Diastolic blood pressure readings for a sample of 200 men 4 6 4 79 are approximately normally distributed with mean 70. One 5 5 hundred and thirty-six (136) of the men had readings 5 7 5 8 between 55 and 85. Use the 68/95/99.7 rule to decide which of the following is closest to the standard deviation of the a) The mean is appropriate I, & the median for II. blood pressure readings. b) The median is appropriate for I, & the mean for II. a) 1 b) 15 c) 30 d) 45 e) 90 c) The median is appropriate for I and for II. d) The mean is appropriate for I and for II. e) Both b) and c) are correct.

3 Scores on a commonly used IQ test are approximately normally distributed with mean 100 and standard deviation 15. In a group of 1000 people, about how many would have IQ's above 115? a) about 5 b) about 25 c) about 50 d) about 160 e) some other number