GIPE Sample Paper

[Kajol]

Can anyone please explain this question?

The length of time it takes college students to find a parking spot in the library parking lot follows a normal distribution with a mean of 4.5 minutes and a standard deviation of 1 minute. The cut-off time which 75.8% of the college students exceed when trying to find a parking spot in the library parking lot is -------. ( Correct to 1 decimal place ).

A) 5.3 min
B) 4.8 min
C) 5.2 min
D) 3.8 min

[Falcon X]

75.8% "exceed" is the same as 100% - 75.8% = 24.2% do not exceed

P(Z < z*) = 0.242 has a z* = -0.70 from Standard Normal table.

Hence the ans is 5.5 + (-0.70)(1) = 4.8 minutes.

So, 75.8% of students exceed 4.8 minutes.

[Neha Gupta]

can anybody suggest how to proceed in paper for such ques. when z table is not given?
or do we simply need to memorize some values?