HELP!!!
The box plots below show attendance at a local movie theater and high school basketball games.
Which of the following best describes how to measure the spread of the data?

- KitKat16

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- KitKat16

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- KitKat16

A: The IQR is a better measure of spread for movies than it is for basketball games.
B: The standard deviation is a better measure of spread for movies than it is for basketball games.
C: The IQR is the best measurement of spread for games and movies.
D: The standard deviation is the best measurement of spread for games and movies.
I know it can't be A or D

- KitKat16

I think it is B because it has a bigger spread.

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## More answers

- anonymous

The problem with the standard deviation in this case is that there is no way to calculate it - we don't have the mean in this problem, so it is not possible to do the calculation without more information.

- Nurali

i think The standard deviation is the best measurement of spread for games and movies.

- KitKat16

So IQR? Is that called a H- spread? What is the H do you know?

- anonymous

@Nurali How would we know this without knowing the mean or standard deviation?

- anonymous

@KitKat16 H-spread is the same as the IQR, but I'm not sure what it stands for. Let me hunt a little.

- anonymous

H seems to stand for "hinge," because Q3 is sometimes referred to as the "upper-hinge" and Q1 is the "lower hinge." The difference Q3-Q1 is the spread between them, hence "H-spread"

- KitKat16

Oh thank you Ive been trying to figure that out

- KitKat16

So in order to know this answer we would need to know mean or standard deviation?

- KitKat16

@Nurali I know that D is wrong

- KitKat16

So I thought it had to be : The standard deviation is a better measure of spread for movies than it is for basketball games

- KitKat16

@ganeshie8 can you look at this for me please?

- anonymous

I think we have to assume that this is all the information we are given. In which case, it wouldn't make sense to choose the options with standard deviation because we know nothing about them.
I believe that C must be the correct answer because there isn't really an alternative (unless there is some information I'm missing).

- welshfella

Is the width of the box indicative of smaller standard deviation. (I never did these before so i'm no expert!) Just a thought

- KitKat16

I thought the box was to show the quadrants

- welshfella

Do the 2 ends of the box give the upper and lower quartiles?

- welshfella

- if so then the IQR for movies is less that that for games.

- KitKat16

spacings between the different parts of the box indicate the degree of dispersion (spread) and skewness in the data, and show outliers.

- welshfella

so maybe A?

- anonymous

@welshfella The two ends of the box do give the measure of spread, but based on the median rather than the mean
Since we know nothing about the mean or standard deviation, the only measure of spread we have is this box-and-whisker plot

- welshfella

the line in the box is the median right?

- anonymous

Correct

- anonymous

Plus, the standard deviation is also strongly swayed by outliers - it seems as though there might be some in this data set

- KitKat16

So this would mean standard deviation is out all together and it would have to be
The IQR is the best measurement of spread for games and movies.

- anonymous

Which means the standard deviation also would not be as good as the IQR

- welshfella

so its A or C?

- anonymous

I would say that C is a better answer, mostly because there is no reason to reject the IQR based on the information given

- anonymous

They are both skewed data sets, which makes them better candidates for the IQR than standard deviation

- anonymous

I suppose you could draw that conclusion about the standard deviation

- anonymous

The standard deviation is mostly used in situations that look relatively unskewed

- anonymous

*I believe

- welshfella

in teresting

- anonymous

In the last paragraph, this article makes the same point about skewed data:
https://epilab.ich.ucl.ac.uk/coursematerial/statistics/summarising_centre_spread/measures_spread/comparing%20measures%20of%20spread.html
And about 60% of the way down on this one
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3198538/

- KitKat16

Thanks so much guys! I wish when I got something wrong the teacher would explain why. This stuff is too confusing.

- welshfella

https://www.youtube.com/watch?v=2v8T96dnmGk
this should help

- welshfella

Note that the data is more skewed for the movies than the games.

- KitKat16

That was awesome @welshfella still confused on the IQR explanation on being less consistant. will watch some more. Thanks again

- welshfella

yw - well if you look at our data the movie data is more consistent than the games data.

- welshfella

I'm not convinced that C is the correct answer. But you said you knew it was'nt A?

- KitKat16

That would make the answer A even though you could measure both best with the IQR

- KitKat16

Thats just what I was thinking

- KitKat16

I know but you know sometimes these questions are faulty

- welshfella

Yea - I'd love to see what the answer is. Its a long time since I did this stuff thats why I@m so hazy about it.

- KitKat16

If I find Out I will let you know and post it here

- welshfella

good ty

- KitKat16

Thanks so much!

- welshfella

yw

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