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Statistical Inference
see this: when it's Z>1.342 that symbol before 1.342 means the corresponding value of z from the table -
Statistical Inference
oh you asked IF it says less than? sorry I misread if it says less than, then we don't subtract the answer is the final answer get that? -
Statistical Inference
no the question is 'more than' but before subtracting, our answer is for at that point or less than that, you could say it says AT LEAST 2500, which covers 2500 and everything less than that. Since 1 is total, subtracting from 1 will mean we get all which is not 'less than' and not less than is... -
Statistical Inference
why not? Leave the logic for a while, you just have to remember that if question asks for 'greater than' find in the normal way, then subtract from 1 at the end, that will get you the 'greater than' -
Statistical Inference
It's a rule that when we find z value at a certain point like at 2500 in part a, the answer we are getting is for values that lie under 2500, i.e. less than 2500. If we have all those less than that value, and the total is always 1, what do we get when we subtract from the total 1? probably the... -
Statistical Inference
but you have to see if they give you negative ones in exam or not so prepare accordingly We don't get negative values -
Statistical Inference
Okay see, if we want an ACCURATE answer, instead of taking 1.65 which corresponds to 0.9505, we can take 1.645 that will mean between 1.64 and 1.65, and it will be correct because our value of 0.95 lies in the middle of 0.9495 and 0.9505, so 1.645 will get us a more correct answer -
Statistical Inference
I don't know if the answer is correct, without the answers, there is no certainty -
Statistical Inference
Q28: We get that damn z value again (will have to go in reverse order in table) We are given mean, sd and the z-value, putting them into formula, we have: 0.95 = (X-26889/ 4500) at 0.95, it's actually (0.9505 but it'll do) it comes under 1.6 from the right and in the 5 from the top so, 1.65 =... -
Statistical Inference
Q42 c) 1000-1994/450 = -2.20 at 2.20 table shows: 0.9861 but that's for 2.20 not for -2.2, (when we get a negative value, we simply subtract the positive from 1 to get the negative, because we are only given positive values in the table in exam and not the negative) so 1 - 0.9861 (for -2.20)... -
Statistical Inference
I think that's in S2, I've just studied S1 yet for my AS :p -
Statistical Inference
you try part c, done the same way, it's just soo easy, give it a try, I'll post the solution then match -
Statistical Inference
yep doing oh there is part c too? wait a bit -
Statistical Inference
b) Between 2500 and 3000 2500-1994/450 < Z < 3000-1994/450 (It means nothing but just that we are finding values between 2500 and 3000, so on one side we find for 2500 and on the other for 3000) 1.12 < Z < 2.23 see... -
Statistical Inference
We go in the reverse order when we have the z value and we have to find x value. For example, when we are given mean, standard deviation and the X as well. Then, we see the z-value and see which x-value it corresponds to. You will see this in Q42. Here is how we solve it: mean= 1994 sd =... -
Statistical Inference
yes sure, I just did 42, let me post that first -
Statistical Inference
Without that we have z-value for 0.7995 not 0.8. We need the value for 0.8. Add 0.005 to 0.7995 in your calc, you'll get 0.8, which is the value we are looking for. So if we add a 3rd digit of 5 in the z-value, it will get us 0.8 exactly -
Statistical Inference
We are finding z value for 0.8. Find in the table where 0.8 is not the 0.8 in the right most row (that's the z-value) we have the x value and we have to correspond that to the z-value and see which z-value it coresponds to: See in the red box 0.7995, that's the nearest to 0.8 we have got in the... -
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