[95_alim]

can someone kindly explain how i answer this question (in attachment) im very confused and dont know how to solve it.

so far i done:



but what is the 0.03 and how do i go from here on.

all help appreciated

thanks

[Azland]

(Original post by 95_alim)
can someone kindly explain how i answer this question (in attachment) im very confused and dont know how to solve it.

so far i done:



but what is the 0.03 and how do i go from here on.

all help appreciated

thanks

Take the Z value of 0.97 and put a - sign




I could be wrong, let someone else confirm what I've done.

[95_alim]

(Original post by Azland)
Take the Z value of 0.97 and put a - sign




I could be wrong, let someone else confirm what I've done.

ok but can u tell me why its -1.88 and not 1.88?

you maybe right in your working.

[Azland]

(Original post by 95_alim)
ok but can u tell me why its -1.88 and not 1.88?

you maybe right in your working.

-Z = 1 - P(Z)

You want the value for 3% so in that case 1 - P(97) = 3%

Also, if you notice in your question that if you took a positive Z, your SD would be negative which isnt possible.

[95_alim]

(Original post by Azland)
-Z = 1 - P(Z)

You want the value for 3% so in that case 1 - P(97) = 3%

Also, if you notice in your question that if you took a positive Z, your SD would be negative which isnt possible.

hmm kinda makes sense

[95_alim]

can anyone confirm if the answer provided is correct?

[Azland]

(Original post by 95_alim)
can anyone confirm if the answer provided is correct?

Why dont you just check the mark scheme or the answer sheet from wherever you got the question from.

[dz287]

a) working out the standard deviation:

The general formula is usually
Z = (X - mean) divided by the standard deviation.

0.03 is basically the Probability of jars having contents weighing less than 100 grams (3% as they said in the question)

From the question we know that:
X = 100g
Mean = 108g
Probability = 0.03

So now we need to know the Z value...
You can find this out using a Z value calculator on the Internet or from a table of values given to you from your textbook maybe. The Z value for 0.03 = -1.880792

So now plug in your numbers into the formula:
-1.880792 = (100 - 108)/standard deviation

Then re-arrange to get your standard deviation:

Standard deviation = (100 - 108)/-1.880792

And that should give you your answer

Hope that helps

[95_alim]

(Original post by dz287)
a) working out the standard deviation:

The general formula is usually
Z = (X - mean) divided by the standard deviation.

0.03 is basically the Probability of jars having contents weighing less than 100 grams (3% as they said in the question)

From the question we know that:
X = 100g
Mean = 108g
Probability = 0.03

So now we need to know the Z value...
You can find this out using a Z value calculator on the Internet or from a table of values given to you from your textbook maybe. The Z value for 0.03 = -1.880792

So now plug in your numbers into the formula:
-1.880792 = (100 - 108)/standard deviation

Then re-arrange to get your standard deviation:

Standard deviation = (100 - 108)/-1.880792

And that should give you your answer

Hope that helps

yh has definitely helped.

thanks

[Azland]

(Original post by 95_alim)
yh has definitely helped.

thanks

I guess he confirmed my answer

[dz287]

(Original post by 95_alim)
yh has definitely helped.

thanks

No Problem ^^

[chloe2]

does anyone have the OCR AS jan 2012 S1 paper and mark scheme by any chance?