# PMF

• Feb 27th 2011, 04:42 AM
Probability Mass Function
At Fred's Automotive works the arrivals of customes at the Desk is timed.Let X= the number of minutes between successive disgruntled customers. It's found that cumulative distribution function of X is:
F(x)= 0 if x<1
F(x)=0.3 if 1<=x<3
F(x)=0.4 if 3<=x<4
F(x)=0.45 if 4<=x<6
F(x)=0.60 if 6<=x<12
F(x)=1 if 12<=x

What is the pmf of X?
Many thanks to everyone who try to help.
• Feb 27th 2011, 10:01 AM
mr fantastic
Quote:

At Fred's Automotive works the arrivals of customes at the Desk is timed.Let X= the number of minutes between successive disgruntled customers. It's found that cumulative distribution function of X is:
F(x)= 0 if x<1
F(x)=0.3 if 1<=x<3
F(x)=0.4 if 3<=x<4
F(x)=0.45 if 4<=x<6
F(x)=0.60 if 6<=x<12
F(x)=1 if 12<=x

What is the pmf of X?
Many thanks to everyone who try to help.

I suggest you start by reviewing the relationship between the cdf and pmf of a discrete random variable (I say discrete since your use of the acronym pmf implies this).

Then post what you can do and say where you get stuck.