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# Normal distribution Q10 Watch

1. I didn't know how to do any of these.

For part i) i tried:

X~ N(1.34, 0.021)
P(x>1.37)
z=(1.37-1.34)/sqrt(0.021)=0.20702

so p(z> 0.20702) = 1- 0.5425 (from the normal distribution tables for 0.20702)

but it was wrong!!

i) 0.077
ii) 0.847
iii) 0.674
iv)1.313m
2. (Original post by 0utdoorz)

I didn't know how to do any of these.

For part i) i tried:

X~ N(1.34, 0.021)
P(x>1.37)
z=(1.37-1.34)/sqrt(0.021)=0.20702

so p(z> 0.20702) = 1- 0.5425 (from the normal distribution tables for 0.20702)

but it was wrong!!

i) 0.077
ii) 0.847
iii) 0.674
iv)1.313m

Notice that, your square rooting in wrong, you've being told the standard deviation, the variable should be std deviation squared so X~N(1.34,0.021^2)
3. (Original post by Robbie242)
Notice that, your square rooting in wrong, you've being told the standard deviation, the variable should be std deviation squared so X~N(1.34,0.021^2)

thanks! I've worked out part i,ii and iii now

how would I do part iv?
4. (Original post by 0utdoorz)
thanks! I've worked out part i,ii and iii now

how would I do part iv?
Notice that 0.10000... is in the percentage points table, once you standardise using the z formula, try to inverse the z results (i.e. negative)
5. (Original post by Robbie242)
Notice that 0.10000... is in the percentage points table, once you standardise using the z formula, try to inverse the z results (i.e. negative)

by standardising using the z formula, do you mean p(x< (L-1.34)/0.021) =0.1?
6. (Original post by 0utdoorz)
by standardising using the z formula, do you mean p(x< (L-1.34)/0.021) =0.1?
Yup then make if that helps (find z on the percentage tables)

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