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GCSE Cumulative Frequency - what do you get?

I've attached a question from a specimen paper for the new GCSE.

I'm interested in what people think the answer is. What would be your two criticisms?

Cumul-freq.pdf40.7KB

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Reply 1

Zacken

Original post by notnek

I've attached a question from a specimen paper for the new GCSE.

I'm interested in what people think the answer is. What would be your two criticisms?

The way I would approach this would be to start plotting my own graph to see if any differences emerge and surely enough, the blindingly obvious one is that there's an error in plotted points; the 46 should be a 48. But, other than that (it's been a long time since I've done these) the only other thing I can think of is either the curve should be a smooth curve and not polygonal or that the mark-axis should have stuff plotted at the end of the class intervals instead of the midpoint. But I don't really remember this stuff, so, bleh.

Reply 2

Notnek

Original post by Zacken

the blindingly obvious one is that there's an error in plotted points; the 46 should be a 48.

Admittedly I didn't spend long thinking about this but my answers at first glance were

1) Not plotted at the ends of the intervals
2) Not a smooth curve

Hopefully if I was doing the exam I would have spotted the incorrect point!

So 2) would not have given me the mark according to the mark scheme. Surely a curve is better than a polygon for a cumulative frequency graph? You can do so much more with a curve.

It's a rare event when I make a mistake on a GCSE paper so I thought it was worth posting here. I've got a feeling that a lot of people would make the same mistake as me.

Reply 3

atsruser

Original post by notnek

I've attached a question from a specimen paper for the new GCSE.

I'm interested in what people think the answer is. What would be your two criticisms?

1. She's put the points in the wrong place - they should be at the top ends of the ranges on the x-axis.

2. Her penultimate value is wrong.

Reply 4

atsruser

Original post by notnek

So 2) would not have given me the mark according to the mark scheme. Surely a curve is better than a polygon for a cumulative frequency graph? You can do so much more with a curve.

That may be the case, but I think all GCSE boards accept both (maybe ?) So it's not an error.

Reply 5

Zacken

Original post by notnek

I technically made the same mistake, but I was hesitant to do so because I distinctly recall markschemes allowing "polygonal curves" when I was doing my (I)GCSE's and was asked to sketch the curves ourselves.

But yeah, it's a very "makes sense" answer.

Reply 6

Notnek

Original post by atsruser

That may be the case, but I think all GCSE boards accept both (maybe ?) So it's not an error.

They may accept both but one is still better than the other :smile:

I'd like to see this question in a real exam and see what percentage get both marks.

Reply 7

ithinkitslily

i'd probably say it's not a smooth curve + doesn't include all the data (excludes o-10 and 90-100)

Reply 8

TheConfusedMedic

•

should plot at class boundaries

•

4th value is plotted wrong

Reply 9

junayd1998

Original post by notnek

I've attached a question from a specimen paper for the new GCSE.

I'm interested in what people think the answer is. What would be your two criticisms?

1) Its not a smooth curve
2) It don't start from 0

Is this the new 9 - 1 spec they will be introducing?

Reply 10

junayd1998

Original post by notnek

I've attached a question from a specimen paper for the new GCSE.

I'm interested in what people think the answer is. What would be your two criticisms?

1) Its not a smooth curve
2) It don't start from 0

Is this the new 9 - 1 spec they will be introducing?

Reply 11

_Xenon_

Original post by junayd1998

1) Its not a smooth curve
2) It don't start from 0

Is this the new 9 - 1 spec they will be introducing?

Yep it's so easy

Reply 12

junayd1998

Original post by _Xenon_

Yep it's so easy

Huh? I thought the new 9 - 1 spec is going to me even more difficult than the current spec?

Reply 13

Zacken

Original post by junayd1998

1) Its not a smooth curve
2) It don't start from 0

Is this the new 9 - 1 spec they will be introducing?

Original post by _Xenon_

Yep it's so easy

Unfortunately, the "not a smooth curve" is incorrect. :smile:

Reply 14

_Xenon_

Original post by junayd1998

Huh? I thought the new 9 - 1 spec is going to me even more difficult than the current spec?

It is more difficult.

Reply 15

junayd1998

Original post by Zacken

Unfortunately, the "not a smooth curve" is incorrect. :smile:

So if you drew a cumulative frequency graph that looked like that it would be okay? :tongue:

Reply 16

Notnek

Original post by junayd1998

So if you drew a cumulative frequency graph that looked like that it would be okay? :tongue:

Yes if you drew a graph like that in an exam you would get the marks.

But I agree with you that not being a smooth curve is a fair criticism - the examiners don't agree with me though.

Don't worry though I doubt they will repeat this question in the real exam.

Reply 17

junayd1998

Original post by notnek

I don't need to worry, I'm doing the old spec for the last time. Quickly escaped from the scary 9 -1 spec that is soon to come.

Reply 18

Asuna Yuuki

There's a lot of problems that you could highlight to be fair.

- incorrectly plotted point
- line should pass through origin
- not a smooth curve
- cumulative values should be plotted at upper class boundary

The last one is a particularly important point which most people missed. That's what would definitely need changing when plotting a CF graph.