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Calling Misc Mathematicians

black gerbil1 Avatar
8y, 6m agoPosted 8 years, 6 months ago
a) A student travels by bus to get to school. On twenty-two separate occasions, she makes a note of the length of time she has to wait for the bus to arrive. The results are shown below in table Q9a:


Waiting time (mins)
time in Minutes:4 5 6 7 8 9
No. of times :2 4 7 6 2 1
Table Q9a

Calculate the mean and standard deviation of the waiting time.

I can do the mean, but wtf the standard deviation.
black gerbil1 Avatar
8y, 6m agoPosted 8 years, 6 months ago
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#1
I don't feel like doing your homework!
#2
Abvance
I don't feel like doing your homework!

lol @ homework, what am i 13?

im doing a past paper, and i have no idea what Standard Deviation is, I looked it up on Wikipeida, and still dont know, so I was hoping it someone would break it down.

kthnxbai
#3
do you want to know what the standard deviation for this question is or what standard deviation is?
#4
guerilla
do you want to know what the standard deviation for this question is or what standard deviation is?


yes the answer is 2.42, but I dont know you would get it.

the mean is 3.67
1 Like #5
banned#6
The sum of x^2/n - mean^2. Then square root it.
#7
This link explains it quite well

http://hubpages.com/hub/stddev
#8
The standard deviation is a statistic that tells you how tightly all the various pieces of data are clustered around the mean in a set of data.

http://upload.wikimedia.org/math/5/e/3/5e31c9f1a59269a8f5d6dda37d8729db.png

http://upload.wikimedia.org/math/f/3/4/f3467b0e7debc2862ad426a63a6838b0.png
#9
the standard deviation is a measurement of the spread of data from the mean. A high standard deviation means the mean is less accurate. If you have a scientific calculator you can work it out using that, the manual should show you how. Alternatively there is an equation what is shown in the link above. If its a past paper it may not be in your syllabus anymore so you may not have to learn it probably better to check.
#10
Murielson

thanks just what i needed raped!
#11
guerilla
The standard deviation is a statistic that tells you how tightly all the various pieces of data are clustered around the mean in a set of data.

http://upload.wikimedia.org/math/5/e/3/5e31c9f1a59269a8f5d6dda37d8729db.png

http://upload.wikimedia.org/math/f/3/4/f3467b0e7debc2862ad426a63a6838b0.png


I dont work for Nasa:p
#12
it was no more difficult that murielson's reply, you need the grouped data equation from the page murielson posted
#13
black gerbil1
thanks just what i needed raped!

:giggle:
#14
Hi black Gerbil,

You say that you can work out the mean, and have 3.67. How can that be right for the average wait time when the time ranges from 4 to 9?
#15
adzcool
Hi black Gerbil,

You say that you can work out the mean, and have 3.67. How can that be right for the average wait time when the time ranges from 4 to 9?


No. of times :2 4 7 6 2 1

is what you do the average by:thumbsup:
#16
It might be easier for you to understand this question if you right the times out like so:

4, 4, 5, 5, 5, 5, 6, 6, 6, 6, 6, 6, 6, 7, 7, 7, 7, 7, 7, 8, 8, 9
#17
I think you have to mutiply each number of times to the correlating waiting time and then do the mean
#18
http://www.ltcconline.net/greenl/courses/201/descstat/meanSDGrouped.htm

a nice example similar to your question with a little applet to check your answers
#19
black gerbil1
No. of times :2 4 7 6 2 1

is what you do the average by:thumbsup:


but that doesnt give you the average waiting time
#20
2 4 7 6 2 1 simply adds to 22 which is the number of times she waited not the actual waiting times
#21
i get mean = 6.23
and sd = 1.27
#22
lolz st4nd4rd d3v!at!0nz :P
i could never get to grips with this stuff, glad i left maths at the door at GCSE!
#23
black gerbil1
No. of times :2 4 7 6 2 1

is what you do the average by:thumbsup:


You are trying to find the average time waiting for the bus not the average of the number of no. of times?!

Look at my previos post.
banned#24
What level are you studying?
#25
JDeal
What level are you studying?

CIA level


, i know how to do it know thanks to http://www.hotukdeals.com/item/183482/calling-misc-mathematicians/showpost.php?p=2081012&postcount=6
as well as others:thumbsup:
#26
black gerbil1
CIA level


, i know how to do it know thanks to http://www.hotukdeals.com/item/183482/calling-misc-mathematicians/showpost.php?p=2081012&postcount=6
as well as others:thumbsup:


off topic but remember that bodybuilding website u linked in magicbeans gym workout thread the other day, i didnt realise u were a member was just goin thru and i saw ur name and though oh black gerbil lol
banned#27
black gerbil1
CIA level


, i know how to do it know thanks to http://www.hotukdeals.com/item/183482/calling-misc-mathematicians/showpost.php?p=2081012&postcount=6
as well as others:thumbsup:


As you can't give me a straight answer, I am not inclined to offer any further advice. However, my guess is you are at GCSE level. If you are doing anything below the higher teir, don't worry about SD. If you are doing A Level or Higher teir GCSE - you have little hope.
#28
JDeal
As you can't give me a straight answer, I am not inclined to offer any further advice. However, my guess is you are at GCSE level. If you are doing anything below the higher teir, don't worry about SD. If you are doing A Level or Higher teir GCSE - you have little hope.


haha you trying to get me mad bra:roll:

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