(maths)統計Eng

hooki

2013-10-05 9:12 pm

Below is the information of the invoices of a company. The sizes and errors of
the invoices are shown below.

Errors
Size of invoicesYes NoTotal
Large 25 20 45
Small 154055
Total4060100

Find:
(a)the probability that the selected invoice is of small size.

(b)the probability that the selected invoice is of large size and it contains no errors.

(c)the probability that the selected invoice is of small size if the invoice contains errors.

(d)the probability that the selected invoice is of large size if the invoice contains no errors.

(e)whether the size of invoice is independent with the errors?

更新1:

求式+答案!!!!唔該

更新2:

As P(Large) * P(Contains errors) <> P(Large and contains errors <> * 以上這2符號是甚麼意思?咩係<>同*

回答 (1)

myisland8132

2013-10-05 11:23 pm

✔ 最佳答案

(a) Probability that the selected invoice is of small size

= 55/100

= 11/20

(b) Probability that the selected invoice is of large size and it contains no errors

= 20/100

= 1/5

(c) Probability that the selected invoice is of small size if the invoice contains errors

= 15/40

= 3/8

(d) Probability that the selected invoice is of large size if the invoice contains no errors

= 20/60

= 1/3

(e) Condiser the invoice which is large size and contains errors

P(Large) = 45/100 = 9/20

P(Contains errors) = 40/100 = 2/5

P(Large and contains errors) = 25/100 = 1/4

As P(Large) * P(Contains errors) <> P(Large and contains errors)

The size of invoice is dependent with the errors

2013-10-07 00:12:01 補充：
<> 表示不等於

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