Ask Me Help Desk - Mathematics : Statics

Mathematics : Statics

I am unable to workout the following problem. Please help:

Compute the mean, median, mode, quartiles, range, variance and standard deviation deviation of the following:

Data Frequency

25 30

40 50

60 20

75 40

93 30

This is the only given information. Thank you for you help.

Masom

I am unable to workout the following problem. Please help:

Compute the mean, median, mode, quartiles, range, variance and standard deviation deviation of the following:

Data Frequency

25 30

40 50

60 20

75 40

93 30

This is the only given information. Thank you for you help.

Masom

Thank you for taking the time to copy your homework to AMHD.
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Well, I'll say what I know.

Mean is the average. If you have 1, 2, 3, 4, 5 at frequencies of 2, 5, 7, 3, 2 respectively, you do ((1*2)+(2*5)+(3*7)... +(5*1))/(2+5+7+3+2)

Median in the middle value. For the above example, you have a total of 19 values (sum of frequencies) The median value is the middle value, that is the 10th value, which is found to be 3. The values from above are : 1, 1, 2, 2, 2, 2, 2, 3, 3, 3,. 5, 5. The 'middle' value is 3.

The mode is the value which appears the highest number of times. In my example, the mode is 3, having the highest frequency of 7.

I don't know variance and std deviation yet. I do have the formulae, but I'm not yet sure how to use them properly.

My guess would be that you need to change that frequency to a relative frequency. That is, the percent of the total. Total the frequencies and take each one and divide by that total. That gives you the frequency as a probability that that data value will happen.

Have you attempted doing the problem? You only said you're having trouble working it out, but what work have you done. Can you post that?

(As a note, columns don't stay when you post, if that's what you were trying to do.)

Quote:

Originally Posted by Unknown008

I don't know variance and std deviation yet. I do have the formulae, but I'm not yet sure how to use them properly.

I have NEVER studied statistics in my life, so I can't shed any light on variance, however the general form for the standard deviation is

$s=sqrt{\frac{\sum_{i=1}^n(x_i-x_m)^2}{n-1}}$

where $x_i$ represents the current data value, n is the total number of data. $x_m$ is your mean.

What the standard deviation is very useful for is to determine the probability of values. Generally 1 standard deviation to the left and right of the bell curve yields 68.2% of the data. 2 standard deviations to the left and right would yield 95.4. You can find out these values by looking either a provided table or charts.

Even though I've never taken a stats course, we run into this a lot in engineering when deciding what pieces of data are outliers.

Also the range is just your lowest value, and your highest value. For example I have a data range {1,5,7,5,5,6,45,5,6,5,68,25,5} then my range is [1,68] using interval notation..

Standard deviation is the square root of a variance. However, there is more than one formula for variance, depending on the type of data you're working with.

Quote:

Originally Posted by morgaine300

Standard deviation is the square root of a variance. However, there is more than one formula for variance, depending on the type of data you're working with.

Hmm... I would understand the practicality of having a standard deviation.. but squaring the value seems a bit arbitrary to me, but that's coming from a viewpoint of someone's whose not taken stats.

Don't think too hard about it. I've never figured out the point of a variance. It's an answer in a homework problem, then take the square root and there's your standard deviation to do all sorts of stuff with. But I've never once actually done anything with the variance itself.

Quote:

Originally Posted by morgaine

Standard deviation is the square root of a variance. However, there is more than one formula for variance, depending on the type of data you're working with.

That is why I prefer not to give the equations for standard deviation and variance now, for I have actually, two, one for grouped data and the other for ungrouped data, which I don't know yet what that actually means.

And there's more than that. :-) There's one for binomials, one for uniform distributions... just off the top of my head. (Plus I'm sure plenty more since I only took one class myself.)

Are you taking stats now? If so, you have now surpassed the level of stuff I had in high school cause that was unavailable. :-) I haven't seen you ask anything about it.

If you want to know about those equations you can PM. Just don't feel like giving all the answers away to OP.

Quote:

Originally Posted by morgaine300

Are you taking stats now? If so, you have now surpassed the level of stuff I had in high school cause that was unavailable. :-) I haven't seen you ask anything about it.

If you want to know about those equations you can PM. Just don't feel like giving all the answers away to OP.

Wait.. is that referring to me? If so, no I'm not taking stats.. yet. I need to finish up the linear algebra course I'm currently taking, then next term I'll be taking stats. But if I'm stuck in a doozy, I'll know where to go, or if not where to go, then at least who to ask :cool:

If that wasn't direct to me, I'm still going to ask now that I know you know hahaha your stuck either way.

Well, if that was directed to me... I'll ask when I have problems, I think it's pointless if I ask something I already know :D

[QUOTE=masom;2046423]I am unable to workout the following problem. Please help:

Compute the mean, median, mode, quartiles, range, variance and standard deviation deviation of the following:

Check out this link. It has all you need - with examples. Good luck cruching all those numbers. You can use a spreadsheet - easier...

Statistics: Measures of Central Tendency - CliffsNotes

I was talking to Unky. It originally followed his post, but then got shoved off onto another page and it wasn't obvious anymore. Sorry.