Thread: Mean

Hey,

Can you guys explain these questions:

60% of the mark is term work and 40% is exam

If yoiu receive a final mark of 76, and receive 70 on the exam, what is your term mark? (All marks are out of 100)

Can you guys explain how you would get the answer? Does it have something to do with weighted mean?

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The mean of a set of numbers is 26, What would the mean be if one of the numbers was increased by 10?



Thankyou

Also, what is the difference with a population mean and a sample mean?
Thanks

Originally Posted by NineZeroFive

Hey,

Can you guys explain these questions:

60% of the mark is term work and 40% is exam

If yoiu receive a final mark of 76, and receive 70 on the exam, what is your term mark? (All marks are out of 100)

Can you guys explain how you would get the answer? Does it have something to do with weighted mean?

final = 0.6*term + 0.4*exam

so:

76 = 0.6*term + 0.4*70

rearranging:

term = (76 - 0.4*70)/0.6 = 80.

------------------------------------

The mean of a set of numbers is 26, What would the mean be if one of the numbers was increased by 10?



Thankyou

Mean = sum/N

if one of the numbers is increased by 10 the new sum s'=s+10, and the
new mean:

mean'=s'/N=(s+10)/N = mean + 10/N

RonL

Originally Posted by NineZeroFive

Also, what is the difference with a population mean and a sample mean?
Thanks

We have a population which might be the heights of all the inhabitants of
Springfield, this with luck will have a mean, we call this the population mean.

We draw a sample of 100 of the inhabitants and calculate their mean height,
this is the sample mean.

RonL

Originally Posted by CaptainBlack

final = 0.6*term + 0.4*exam

so:

76 = 0.6*term + 0.4*70

rearranging:

term = (76 - 0.4*70)/0.6 = 80.




Mean = sum/N

if one of the numbers is increased by 10 the new sum s'=s+10, and the
new mean:

mean'=s'/N=(s+10)/N = mean + 10/N

RonL

Sorry, I forgot to add that there are 5 numbers in the set.

Can someone please explain this ?

Thanks

Originally Posted by NineZeroFive

Sorry, I forgot to add that there are 5 numbers in the set.

Can someone please explain this ?

Thanks

So N=5, and then:

mean' = mean+10/5 = mean+2

RonL

Originally Posted by CaptainBlack

So N=5, and then:

mean' = mean+10/5 = mean+2

RonL

Sorry, I'm not to good with math..

How is mean' different from mean?

Can you please calculate it for me? Thankyou

Also, regarding my first question, can you please show me how the equation gets rearranged? Thanks.

Originally Posted by NineZeroFive

Sorry, I'm not to good with math..

How is mean' different from mean?

Can you please calculate it for me? Thankyou

Also, regarding my first question, can you please show me how the equation gets rearranged? Thanks.

mean is the original mean and mean' is the mean when one value is increased by 10.

RonL

Originally Posted by CaptainBlack

mean is the original mean and mean' is the mean when one value is increased by 10.

RonL

I get 7.2 :S

Originally Posted by NineZeroFive

I get 7.2 :S

mean'=mean+2=26+2=28

RonL

Originally Posted by CaptainBlack

mean'=mean+2=26+2=28

RonL

Why did you add 2?

Originally Posted by NineZeroFive

Why did you add 2?

Because:

mean'=s'/N=(s+10)/N = mean + 10/N

and mean=26, and N=5.

RonL