Please help me with my math homework!! showing range, median, and mode

mantastrike · 2011-05-11 16:50:31

A telephone survey was conducted in Tasmania to find out how many hours a sample of students work on computers per week. The hours were:

31 32 15 14 13 38 18 15 36 26
24 25 18 27 32 32 10 17 23 20
20 22 28 17 10 35 18 34 27 19

a) Compute the sample mean.

b) Compute the range, median and mode

c) Compute the variance, standard deviation and the coefficient of variation of the data

Note: the answers must calculated in a table using a calculator with formulae shown in column headers.

bobbym · 2011-05-11 18:46:14

Hi;

a) The sum is 696 and you have 30 pieces of data. Now how do you get an average? Please try this yourself. You are in a statistics class, you must know how to compute an average.

Please go here:

http://www.mathsisfun.com/mean.html

Can you do it now? If not please explain why.

mantastrike · 2011-05-13 23:38:29

Ok,
a) I got my sample mean which is 696/30 = 23.2
b) Range max hrs usage = 38 minimum is 10 therefore 38-10 = "18" My range is 18 right??

my median is 23.5 "23 and 24" is in the middle however I am confused if I should include the duplicate numbers for example 32, 32, 32 there are 32... I still did include them, can you please tell me If it's alright?

my mode is 18 and 32 is that right? because both 18 and 32 appears 3 times is it right?

c) Now this is the confusing part getting my variance
My mean is 23.2

the formule is 1/n-1
to get N first is = sum of all numbers x (X - mean)^2

I chose 38 as my X
Which is

1/696(38-23.2)^2-1

=

1/152450.84

and the answer is

= 6.55949157x10^-6

What the hell??

How am I supposed to get the SD and the Coefficient of variation if the answer is like that??

bobbym · 2011-05-14 00:16:07

Hi;

a) is correct.

b) Range is incorrect.

b) Median is incorrect.

b) Mode is correct. We say it is bimodal.

c) Variance is wrong. Should get an answer close to 64.3

Please look here:

http://www.mathsisfun.com/data/standard-deviation.html

Bob · 2011-05-14 00:25:49

hi mantastrike

Oh hi bobbym. 'Pipped me to the post again!'

a) I got my sample mean which is 696/30 = 23.2

Yes, I agree with that.

b) Range max hrs usage = 38 minimum is 10 therefore 38-10 = "18" My range is 18 right??

Whoops! Right idea, but your subtraction is wrong!

my median is 23.5 "23 and 24" is in the middle however I am confused if I should include the duplicate numbers for example 32, 32, 32 there are 32... I still did include them, can you please tell me If it's alright?

You are right to keep all duplicates, but these are not the middle numbers.

my mode is 18 and 32 is that right? because both 18 and 32 appears 3 times is it right?

Yes

c) Now this is the confusing part getting my variance
My mean is 23.2
the formule is 1/n-1
to get N first is = sum of all numbers x (X - mean)^2

The correct formula for variance is

Last edited by Bob (2011-05-14 00:35:48)

bobbym · 2011-05-14 00:31:41

Hi Bob;

I have a feeling there is plenty more to come.

mantastrike · 2011-05-14 00:34:00

bobbym wrote:

Hi;
a) is correct.
b) Range is incorrect.
b) Median is incorrect.
b) Mode is correct. We say it is bimodal.
c) Variance is wrong. Should get an answer close to 64.3
Please look here:
http://www.mathsisfun.com/data/standard-deviation.html

b) how come my median is incorrect??

c) Can you please show me how you get the variance and I can take it from there. Please!!

bobbym · 2011-05-14 00:35:20

One thing at a time please, what are the two middle numbers?

mantastrike · 2011-05-14 00:38:05

bob bundy wrote:

hi mantastrike
Oh hi bobbym. 'Pipped me to the post again!'
a) I got my sample mean which is 696/30 = 23.2
Yes, I agree with that.

b) Range max hrs usage = 38 minimum is 10 therefore 38-10 = "18" My range is 18 right??
Whoops! Right idea, but your subtraction is wrong!

my median is 23.5 "23 and 24" is in the middle however I am confused if I should include the duplicate numbers for example 32, 32, 32 there are 32... I still did include them, can you please tell me If it's alright?
You are right to keep all duplicates, but these are not the middle numbers.
my mode is 18 and 32 is that right? because both 18 and 32 appears 3 times is it right?
Yes
c) Now this is the confusing part getting my variance
My mean is 23.2
the formule is 1/n-1
to get N first is = sum of all numbers x (X - mean)^2
The correct formula for variance is

Thanks for the correction! PHEW!! why is my middle number incorrect? half of 30 is 15 but still... If I consider 23 as middle number the numbers left on the right side is 14 numbers left so the middle is "23.5"

PLEASE HELp me...

Bob · 2011-05-14 00:38:10

Just read your last post. There are 30 numbers so the middle two are the 15th and 16th. Then take the value half way between.

There are two variances that could be calculated: the sample variance and the estimatedpopulation variance. I have assumed the question wants the first of these.

I've put a corrected formula for vaiance in my previous post.

bobbym: I'm assuming this question wants the vaiance of these figures. It doesn't mention extmating population values from a sample.

Bob

Last edited by Bob (2011-05-14 00:52:13)

bobbym · 2011-05-14 00:40:37

That is what I am going to do, just as soon as he gets the median.

mantastrike · 2011-05-14 00:42:53

I got the median... I missed count... it's 23

bob the formula you gave me? what the hell is that thing?? noooooooooooooo!!

Bob · 2011-05-14 00:44:35

Still don't agree with this median. What are you using for 15th and 16th numbers?

That's the formula for variance.

It means square each x, add them up, divide by 30, subtract the square of the mean.

Bob

Last edited by Bob (2011-05-14 00:50:45)

bobbym · 2011-05-14 00:46:32

Hi;

That is not the median from what I have. What is the 15th piece of data and the 16th?

mantastrike · 2011-05-14 00:56:26

I arranged it it goes like this

10,10,13,14,15,17,17,18,18,18,19,20,20,22,23,24,25,26,27,27,28,31,32,32,32,34,35,36,38

middle is 23 and 24 right?
and then 23+24/2 = "23.5"

How is my median incorrect?

bobbym · 2011-05-14 00:59:59

You are missing a 15!

{10,10,13,14,15,15,17,17,18,18,18,19,20,20,22,23,24,25,26,27,27,28,31,32,32,32,34,35,36,38}

mantastrike · 2011-05-14 01:08:03

so that's why! ok it's 22.5?

Now how do I get the variance? I have no Idea what is that formula?

bobbym · 2011-05-14 01:16:18

For a sample variance

For a population variance:

With x = the data, m = mean, n = 30.

I would go with the sample one here. I am getting 64.303

Use this page for the calculations.

http://easycalculation.com/statistics/s … iation.php

mantastrike · 2011-05-14 01:25:33

is the reverse letter E is what you call variance?
my mean is 23.2, my n = 30, how can I get that reverse E and the x?

so my E = (38-23.2)^2???????
n????????????????

so... it does not = 64.3 something

Ah how can I get this??
can you please show me this one? so I can finish this... I have no Idea how can I do this

Last edited by mantastrike (2011-05-14 01:27:16)

bobbym · 2011-05-14 01:27:53

That E is an operator, it means sum them up. First did you use the page I gave you?

mantastrike · 2011-05-14 01:36:00

Yes I did, I got same answer? But how am I supposed to show workings??

Last edited by mantastrike (2011-05-14 01:37:04)

bobbym · 2011-05-14 01:45:54

There is no easy way to show the work. It is a a job for a calculator or computer. All I can give you is the method but there is a lot of calculation involved.

http://www.statisticshowto.com/calculat … alculator/

For a step by step method that gets my answer.

Square the 30 numbers and add them up you get 18012, then add the 30 numbers and sqaure the answer and divide by 30 you get 80736 / 5. Subtract these two numbers and divide by 29.

mantastrike · 2011-05-14 02:01:58

coefficient of variant is not included? how do I get it??

bobbym · 2011-05-14 02:33:55

Use this formula:

mantastrike · 2011-05-14 02:44:11

Thanks for all your help you 2, I finish and I am submitting tomorrow.
By the way I have a question...

What are the chances of getting caught for plagiarism.
Most help I get are like too advance? which I cannot figure out how they were able to answer it, therefore I have no Idea about the answer.

Is it possible if a university teacher may call me and ask where am I getting answers? And would want how I got the answer?

Is it OK to ask for help if it's homework??

for example gAr's answer is straight away an answer and I just copied... For sure it's correct. Would teacher sue me?

Math Is Fun Forum

#1 2011-05-11 16:50:31

Please help me with my math homework!! showing range, median, and mode

#2 2011-05-11 18:46:14

Re: Please help me with my math homework!! showing range, median, and mode

#3 2011-05-13 23:38:29

Re: Please help me with my math homework!! showing range, median, and mode

#4 2011-05-14 00:16:07

Re: Please help me with my math homework!! showing range, median, and mode

#5 2011-05-14 00:25:49

Re: Please help me with my math homework!! showing range, median, and mode

#6 2011-05-14 00:31:41

Re: Please help me with my math homework!! showing range, median, and mode

#7 2011-05-14 00:34:00

Re: Please help me with my math homework!! showing range, median, and mode

#8 2011-05-14 00:35:20

Re: Please help me with my math homework!! showing range, median, and mode

#9 2011-05-14 00:38:05

Re: Please help me with my math homework!! showing range, median, and mode

#10 2011-05-14 00:38:10

Re: Please help me with my math homework!! showing range, median, and mode

#11 2011-05-14 00:40:37

Re: Please help me with my math homework!! showing range, median, and mode

#12 2011-05-14 00:42:53

Re: Please help me with my math homework!! showing range, median, and mode

#13 2011-05-14 00:44:35

Re: Please help me with my math homework!! showing range, median, and mode

#14 2011-05-14 00:46:32

Re: Please help me with my math homework!! showing range, median, and mode

#15 2011-05-14 00:56:26

Re: Please help me with my math homework!! showing range, median, and mode

#16 2011-05-14 00:59:59

Re: Please help me with my math homework!! showing range, median, and mode

#17 2011-05-14 01:08:03

Re: Please help me with my math homework!! showing range, median, and mode

#18 2011-05-14 01:16:18

Re: Please help me with my math homework!! showing range, median, and mode

#19 2011-05-14 01:25:33

Re: Please help me with my math homework!! showing range, median, and mode

#20 2011-05-14 01:27:53

Re: Please help me with my math homework!! showing range, median, and mode

#21 2011-05-14 01:36:00

Re: Please help me with my math homework!! showing range, median, and mode

#22 2011-05-14 01:45:54

Re: Please help me with my math homework!! showing range, median, and mode

#23 2011-05-14 02:01:58

Re: Please help me with my math homework!! showing range, median, and mode

#24 2011-05-14 02:33:55

Re: Please help me with my math homework!! showing range, median, and mode

#25 2011-05-14 02:44:11

Re: Please help me with my math homework!! showing range, median, and mode

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