→ LITTLEN:a. z=-1.28 b跟c.z取多一點小數就好..我改的話bc給你對=.= 01/15 02:47
The U.S. Bureau of Labor Statistics reports that the average annual
expenditure on food and drink for all families is $5700 . Assume that annual
expenditure on food and drink is normally distributed and that the standard
deviation is $1500.
a. How much do the 10% of families with the lowest expenditure level spend
annually on food and drink?
b. What percentage of families spend more than $7000 annually on food and
drink?
c. How much do the 5% of the families with the highest expenditure level
spend annually on food and drink?
a.
我利用z=(x-μ)/σ算的
他的意思應該是說消費階層最低的10%每年消費在飲食上的金額是多少?
題目的μ=5700 σ=1500
z=(x-5700)/1500=-0.1
x=5550
但答案是3780= =
b.求p(x≧7000)=p(z≧0.86)=0.500-0.3051=0.1949
但答案是0.1922....
c.z=1.96=(x-5700)/1500
x=8140
但答案是8167.5= =
拜託高手解題~
謝謝:)
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※ david7834:轉錄至看板 ask 01/15 02:43