The life time of the Tuff brand of tyres is approximately normally distributed, with a mean of 63,000 km and a standard deviation of 3,000 km. The tyres carry a warranty of 55,000 km.
What proportion of tyres will fail before the warranty expires?
An appropriate, well labelled diagram
must be included.
The Tuff company claims that at least 10% of the tyres last longer than 68,000 km.
Provide evidence to support or disprove this statement.
An appropriate, well labelled diagram
must be included.
Second Question
A switch board operator receives an average of 25 calls every 15 minutes. Calls are received randomly and independently. The switch board operator used the following Excel command to determine a probability 1-POISSON(20, 25, TRUE .
Describe in words or write down using probability notation what probability he worked out in the context of this problem and then use Excel to evaluate it.
What proportion of tyres will fail before the warranty expires?
An appropriate, well labelled diagram
must be included.
The Tuff company claims that at least 10% of the tyres last longer than 68,000 km.
Provide evidence to support or disprove this statement.
An appropriate, well labelled diagram
must be included.
Second Question
A switch board operator receives an average of 25 calls every 15 minutes. Calls are received randomly and independently. The switch board operator used the following Excel command to determine a probability 1-POISSON(20, 25, TRUE .
Describe in words or write down using probability notation what probability he worked out in the context of this problem and then use Excel to evaluate it.
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