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# S1 Question help

1. 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
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2. (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.
3. (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.
4. (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.
5. (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
6. can anyone confirm if the answer provided is correct?
7. (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.
8. 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

Hope that helps
9. (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

Hope that helps

yh has definitely helped.

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

thanks
I guess he confirmed my answer
11. (Original post by 95_alim)
yh has definitely helped.

thanks
No Problem ^^
12. does anyone have the OCR AS jan 2012 S1 paper and mark scheme by any chance?

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