More Probability/Statistics Intro

[SANDRAJOD]

Hi -

An analyst examined some test data for washing machine failures and found the following:
10% of the units failed because of a bad belt
25% of the units failed because of a bad hose
40% of the units failed because of a bad motor
40% of the units failed because of a bad timer
The analyst concluded that the probability of failure was 1.15 (10 + 25 + 40 + 40).
Comment on the analyst's conclusion.

First of all, I disagree because the total is greater than 100%.
What I am unsure of is how to show the correct conclusion.

Your help is much appreciated!
Sandra

 

[chrisr]

Hi SANDRAJOD,

The analyst has failed to take into account

(a) % of units that failed because of both a bad motor and a bad timer
(b) bad motor and bad hose
(c) bad timer and bad belt
(d) all 4 bad
(e) various combinations of 3 bad

If you draw a venn diagram, you can illustrate all the set intersections.
That information has been excluded from the data.
The analyst would have needed some of that to draw accurate conclusions.