Question 223174
The time it takes to travel from home to the office is normally distributed with  {{{mu= 25}}} minutes and {{{sigma = 5}}} minutes.

a.	What is the probability the trip takes more than 20 minutes?
<pre><font size=4 color= "indigo"><b>
        On your TI-83 or TI-84 calculator:

        1.  Press CLEAR
        2.  Press 2ND 
        3.  Press VARS 
        4.  Press 2
        6.  You see normalcdf( 
        7.  After that type in:  20,999999999,25,5) so that what you see
            is this 
            
            normalcdf(20,999
            999999,25,5)

        8.  Press ENTER
        9.  Read the answer .8413447404          

</pre></font></b>
b.	What is the probability the trip takes less than 15 minutes.
<pre><font size=4 color= "indigo"><b>
        1.  Press CLEAR
        2.  Press 2ND 
        3.  Press VARS 
        4.  Press 2
        6.  You see normalcdf( 
        7.  After that type in:  -999999999,15,25,5) so that what you see
            is this: 
            
            normalcdf(-99999
            9999,15,25,5)
            
            Caution: be sure that the "-" is the NEGATIVE sign on the
            very bottom right button, that looks liks this (-), and NOT
            the minus sign above the + button. 
               
        8.  Press ENTER
        9.  Read the answer .022750062
</pre></font></b>
c.	What is the probability the trip takes between 30 and 35 minutes?
<pre><font size=4 color= "indigo"><b>
     1.  Press CLEAR
        2.  Press 2ND 
        3.  Press VARS 
        4.  Press 2
        6.  You see normalcdf( 
        7.  After that type in:  30,35,25,5) so that what you see
            is this 
            
            normalcdf(30,35,
            25,5)

        8.  Press ENTER
        9.  Read the answer .1359051975  

</pre></font></b>
d.	What is the probability the trip takes more than 40 minutes?
<pre><font size=4 color= "indigo"><b>

        1.  Press CLEAR
        2.  Press 2ND 
        3.  Press VARS 
        4.  Press 2
        6.  You see normalcdf( 
        7.  After that type in:  40,999999999,25,5) so that 
            what you see is this 
            
            normalcdf(40,999
            999999,25,5)

        8.  Press ENTER
        9.  Read the answer .0013499672  

If you're supposed to use tables and not a calculator, then
post again telling us whether you have the kind of tables
with both negative and positive z-scores or whether you have
the kind with onl;y positive z-scores.

Edwin</pre>