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S1 question? Help needed..

s1.png
Could someone provide me with clear explanation of how to complete this question.

Many thanks.
Reply 1
Avatar for lerjj
lerjj
13
Original post by greentron6
s1.png
Could someone provide me with clear explanation of how to complete this question.

Many thanks.


What have you done/ tried to do?

The first step with histogram / interval data is to convert the endpoints to true values.

The next thing you need to do for this question is to work out the total number of people >24.5 and the total sample size.
Reply 2
Avatar for googleit
googleit
5
Do what the guy said above then just multiply the probability value you get
Reply 3
Avatar for greentron6
greentron6
OP
11
Original post by googleit
Do what the guy said above then just multiply the probability value you get


:s-smilie: Im still confused. Could you actually do the question for me, so I can understand better...
Reply 4
Avatar for greentron6
greentron6
OP
11
Original post by lerjj
What have you done/ tried to do?

The first step with histogram / interval data is to convert the endpoints to true values.

The next thing you need to do for this question is to work out the total number of people >24.5 and the total sample size.


Thanks for replying!
Im still confused. Could you actually do the question for me, so I can understand better...
Reply 5
Avatar for lerjj
lerjj
13
Original post by greentron6
Thanks for replying!
Im still confused. Could you actually do the question for me, so I can understand better...


P(t>24.5)=8+32+9+20+13+8+3 P (t > 24.5) = \dfrac{ 8 + 3}{2+9+20+13+8+3}
P=0.2 P=0.2
(Because it asks for over 24.5, that's just the last two entries. If it asked for e.g. 24.3 you'd need to interpolate a little instead of just adding up the numbers in the last two boxes)

Edit: Misread the question - it says that there are two phone calls. That means that this is a "drawing without replacement" style question. The probability that the first call is >24.5minutes is still 11/55, but the second call now has a probability of 10/54 since you presumably made sure it wasn't the same call. So the combined probability is 1/27.
(edited 7 years ago)
Reply 6
Avatar for greentron6
greentron6
OP
11
This is new to me. Is this still on the spec?
Original post by lerjj
P(t>24.5)=8+32+9+20+13+8+3 P (t > 24.5) = \dfrac{ 8 + 3}{2+9+20+13+8+3}
P=0.151 P=0.151
(Because it asks for over 24.5, that's just the last two entries. If it asked for e.g. 24.3 you'd need to interpolate a little instead of just adding up the numbers in the last two boxes)


How did you get that answer? I did it with the z = X - Mean / Standard deviation
and the used the probability table to get the answer. Which is 0.56155
Reply 8
Avatar for lerjj
lerjj
13
Original post by greentron6
This is new to me. Is this still on the spec?


Yes, it's a simple probability question.

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