求解OG两道数学题

alongdream · 发表于 2012-9-7 22:19:19

P296
2. The numbers of passengers on 9 airline ?ights were 22, 33, 21, 28, 22, 31, 44,
50, and 19. The standard deviation of these 9 numbers is approximately
equal to 10.2.
(a) Find the mean, median, mode, range, and interquartile range of the 9
numbers.
" interquartile range "该怎么算呢？
P298
14. Let A, B, C, and D be events for which P(A or B)0.6, P(A)0.2,
and The events A and B are mutually exclusive, P(C or D)0.6, P(C)0.5.
and the events C and D are independent.
(b) Find P(D)
P(D)怎么求出来的？

普渡哥 · 发表于 2012-9-8 21:09:00

Interquartile Range
The interquartile range (IQR) is a measure of variability, based on dividing a data set into quartiles.

Quartiles divide a rank-ordered data set into four equal parts. The values that divide each part are called the first, second, and third quartiles; and they are denoted by Q1, Q2, and Q3, respectively.

Q1 is the "middle" value in the first half of the rank-ordered data set.
Q2 is the median value in the set.
Q3 is the "middle" value in the second half of the rank-ordered data set.
The interquartile range is equal to Q3 minus Q1.

For example, consider the following numbers: 1, 3, 4, 5, 5, 6, 7, 11. Q1 is the middle value in the first half of the data set. Since there are an even number of data points in the first half of the data set, the middle value is the average of the two middle values; that is, Q1 = (3 + 4)/2 or Q1 = 3.5. Q3 is the middle value in the second half of the data set. Again, since the second half of the data set has an even number of observations, the middle value is the average of the two middle values; that is, Q3 = (6 + 7)/2 or Q3 = 6.5. The interquartile range is Q3 minus Q1, so IQR = 6.5 - 3.5 = 3.

普渡哥 · 发表于 2012-9-8 21:11:35

第二个应该也是套公式。。。统计课教过。。

dutianandy · 发表于 2012-9-8 22:08:56

interquartile range：就是找四个数，把这组数分成三等份，所以包括最大值，最小值

alongdream · 发表于 2012-9-9 14:49:32

题目里是9个数，Q1、Q3该怎么算？

alongdream · 发表于 2012-9-9 14:53:43

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dutianandy · 发表于 2012-9-9 15:38:17

比如1，2,3,4，5,6,7,8,9
应该是1, 3.5, 6.5, 9四个数

alongdream · 发表于 2012-9-9 16:02:01

公式里还有两个未知量，怎么求？

lylinsong · 发表于 2012-12-8 01:50:09

P(C or D)=P(C)+P(D)+P(C)*P(D)

glacier1985 · 发表于 2012-12-8 23:13:02

P(C or D)=P(C)+P(D)+P(C)*P(D)

-- by 会员 lylinsong (2012/12/8 1:50:09)

这个公式好像错了，应是
P(C or D)=P(C)+P(D)-P(C)*P(D)

[数学] 求解OG两道数学题

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