# S1 chapter 2 question

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So I'm trying to do this question and it should be relatively easy, I just keep getting different answers to the one in the text book. To make it more confusing SolutionBank gets a different answer to what's at the back of the text book as well.

The books got 1.08 and SolutionBank gets 0.722. I get 0.94 so I'm literally so confused right now. Any help would be useful.

*A hotel is worried about the reliability of its lift. It keeps a weekly record of the number of times it breaks down over 26 weeks.**Number of breakdowns - Frequency**0-1 - 18**2-3 - 7**4-5 - 1**b. Use interpolation to estimate the median number of breakdowns.*The books got 1.08 and SolutionBank gets 0.722. I get 0.94 so I'm literally so confused right now. Any help would be useful.

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#3

make sure you grouped the data correctly. check your arithmetic in your calculations and check your cumulative frequency calculations. also check if you've done the linear interpolation method properly, it's easy to mix up two numbers (medianClass -minclass/maxclass-minclass = medianPos - minCumulative/maxCumulative - minCumulative)

it would help if you posted a screenshot of your workings.

it would help if you posted a screenshot of your workings.

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#4

Here is a video I have done on linear interpolation - it goes through each step. Hope this helps!

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#5

I know this is an old forum but this is for anyone who still needs it. The answer on solution bank isn't complete - they forgot to multiply 13/18 by 1.5.

0.722 x 1.5 = 1.08

So just follow the one on solution bank and finish the last step. The key here is that you have got to assume that the width is 0 - 1.5. To be honest I'm still stuck on why this is, since the data isn't "to the nearest week", it is simply after each week.

0.722 x 1.5 = 1.08

So just follow the one on solution bank and finish the last step. The key here is that you have got to assume that the width is 0 - 1.5. To be honest I'm still stuck on why this is, since the data isn't "to the nearest week", it is simply after each week.

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#6

(Original post by

I know this is an old forum but this is for anyone who still needs it. The answer on solution bank isn't complete - they forgot to multiply 13/18 by 1.5.

0.722 x 1.5 = 1.08

So just follow the one on solution bank and finish the last step. The key here is that you have got to assume that the width is 0 - 1.5. To be honest I'm still stuck on why this is, since the data isn't "to the nearest week", it is simply after each week.

**alextheowl**)I know this is an old forum but this is for anyone who still needs it. The answer on solution bank isn't complete - they forgot to multiply 13/18 by 1.5.

0.722 x 1.5 = 1.08

So just follow the one on solution bank and finish the last step. The key here is that you have got to assume that the width is 0 - 1.5. To be honest I'm still stuck on why this is, since the data isn't "to the nearest week", it is simply after each week.

(I'm not sure, by the way - I'm just curious.)

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#7

**alextheowl**)

I know this is an old forum but this is for anyone who still needs it. The answer on solution bank isn't complete - they forgot to multiply 13/18 by 1.5.

0.722 x 1.5 = 1.08

So just follow the one on solution bank and finish the last step. The key here is that you have got to assume that the width is 0 - 1.5. To be honest I'm still stuck on why this is, since the data isn't "to the nearest week", it is simply after each week.

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#8

(Original post by

I disagree with this. The data is discrete so clearly the median has to lie between 0 and 1.

**Notnek**)I disagree with this. The data is discrete so clearly the median has to lie between 0 and 1.

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#9

(Original post by

That is what I thought at first. The book (and kind of solution bank) say 1.08, so I assumed they were correct. Maybe they're both wrong.

**alextheowl**)That is what I thought at first. The book (and kind of solution bank) say 1.08, so I assumed they were correct. Maybe they're both wrong.

Actually since it’s discrete data I would have thought that it should be the 13.5th value and not the 13th.

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#10

(Original post by

The solution bank I’m looking at says it’s 0.722.

Actually since it’s discrete data shouldn’t it be the 13.5th value and not the 13th?

**Notnek**)The solution bank I’m looking at says it’s 0.722.

Actually since it’s discrete data shouldn’t it be the 13.5th value and not the 13th?

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#11

(Original post by

The solution bank forgot to multiply 13/18 by 1.5 to get 1.08. And I'm as confused as you are now, I will ask my teacher on Monday!

**alextheowl**)The solution bank forgot to multiply 13/18 by 1.5 to get 1.08. And I'm as confused as you are now, I will ask my teacher on Monday!

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#12

ghostwalker DFranklin

I’m still not experienced with this kind of thing so do you mind sharing the answer that you get (question in OP) when you have time?

I don’t know if methods for finding medians vary between courses.

I’m still not experienced with this kind of thing so do you mind sharing the answer that you get (question in OP) when you have time?

I don’t know if methods for finding medians vary between courses.

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#13

(Original post by

ghostwalker DFranklin

I’m still not experienced with this kind of thing so do you mind sharing the answer that you get (question in OP) when you have time?

I don’t know if methods for finding medians vary between courses.

**Notnek**)ghostwalker DFranklin

I’m still not experienced with this kind of thing so do you mind sharing the answer that you get (question in OP) when you have time?

I don’t know if methods for finding medians vary between courses.

Tagging Gregorious as the definite stats master of f38...

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#14

(Original post by

The solution bank I’m looking at says it’s 0.722.

Actually since it’s discrete data I would have thought that it should be the 13.5th value and not the 13th.

**Notnek**)The solution bank I’m looking at says it’s 0.722.

Actually since it’s discrete data I would have thought that it should be the 13.5th value and not the 13th.

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#15

**Notnek**)

ghostwalker DFranklin

I’m still not experienced with this kind of thing so do you mind sharing the answer that you get (question in OP) when you have time?

I don’t know if methods for finding medians vary between courses.

__grouped data__, the median is taken to be the (1/2) nth reading, i.e. the 13th.

Interpolation gives us 13/18 = 0.7222..., of the way through the interval.

The $64,000 question is what is the class width, for this

__discrete__data? I would say it's "1", and so 0.722... is the desired value, since the interpolated value must lie between 0 and 1.

**Edit:**On further reflection, this would imply that if the median shifted by one place it could conceivably jump from 1 to 2, if it was at the end of the interval, which doesn't seem right. So, perhaps the class interval should be 2. Making the median 1.444...

Gregorius would be a good person to get on board with this, I think.

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#16

(Original post by

Since we have

Interpolation gives us 13/18 = 0.7222..., of the way through the interval.

The $64,000 question is what is the class width, for this

**ghostwalker**)Since we have

__grouped data__, the median is taken to be the (1/2) nth reading, i.e. the 13th.Interpolation gives us 13/18 = 0.7222..., of the way through the interval.

The $64,000 question is what is the class width, for this

__discrete__data? I would say it's "1", and so 0.722... is the desired value, since the interpolated value must lie between 0 and 1.I doubt this would appear in an A Level exam.

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#17

(Original post by

Thanks. I’m not used to grouped discrete data so was unsure and there may not be a standard A Level method for this.

I doubt this would appear in an A Level exam.

**Notnek**)Thanks. I’m not used to grouped discrete data so was unsure and there may not be a standard A Level method for this.

I doubt this would appear in an A Level exam.

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#18

(Original post by

I changed my mind and updated my previous post - sorry!

**ghostwalker**)I changed my mind and updated my previous post - sorry!

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#19

(Original post by

Does it make sense to have a median greater than 1?

**Notnek**)Does it make sense to have a median greater than 1?

I'm having third thoughts now. Oh, dear.

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#20

I actually thought you would choose (n+1)/2 because it’s discrete data. But I’m not used to grouped discrete data as I’ve said.

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