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Sir I’m really confused about these questions, in bpp kit could you please help me out?
A normal distribution has a mean of 75 and a variance of 25.
What is the upper quartile of this distribution?
-58.25
-71.65
-78.35
-91.75I have no idea what is upper quartile please help me out sir
Q2 a normal distribution is to be split into four equal areas, two to the right of Z= 0 and two to the left of Z= 0 (Z=0 at the mean)
Using normal distribution tables, the |Z| value that splits the area in this way is closest to which of the following?
-0.0987
-0.1915
-0.3333
-0.675099Sir normal distribution has two sides either more or less than mean, 0.5 to right and left both equal, I don’t understand this question as well
And sir last question similar to this
A normal distribution is to be split into eight areas, four to the right of Z=0 and four to the left of Z=0 ( Z=0 at the mean)
Using normal distribution tables, the |Z| value splits the area in this way is closest to which of the following?
-0.28
-0.30
-0.32
-0.341. The upper quartile is the top 25%
2. If there are 4 equal areas, then each area is covering 25%
3. If there are 8 equal areas then each area is covering 12.5%.
Draw a quick picture of the curve each time as I do in my lectures.
Sir i got it the 3rd question, but the 2nd one answer is 0.675099, how? It’s only 0.67 as it shows on normal distribution table, the value of z score
And sir first question, still im confused how is upper quartile 25%? I also don’t get it what is quartile, please could you explain me further, also they’re multiplying the z score of 25% with s.d 5, I don’t get that as well
They have apportioned between 0.67 and 0.68. You do not need to do this in the exam.
A quartile is 25%. So the quartiles are 0 to 25%, 25 to 50%, 50 to 75% and 75 to 100%. The last one is the upper quartile.
Sir sorry for being clumsy, but I’m still getting confused :’), okay i acknowledged those range you said sir but could you please tell me how do we know it’s 25%? Because mean is 75? That’s why the remaining that is quartile? Because you said 75-100 last one is upper quartile, like i know when question tells you to find z score from a % doing it all reverse, but I don’t understand this question, i watched your lecture on this yesterday sir, but i still am facing confusion
Quartile means quarter, and one quarter of 100% is 25%.
For the upper quartile you are being asked for the mark where the probability of being higher than that mark is 25%.
Sir if it would’ve asked to find lower quartile, how would we solve that and also median of quartile? sir all those quartile either upper or lower would always be 25%?
Please could you give me one question on each of these quartile to clear my confusion, I’d really appreciate it
But you have questions in your revision kit.
The first quartile is the mark below which the probability is 25%. The second quartile is where the probability of being between the mark and the mean is 25%. The third quartile is there the probability of being between the mean and the mark is 26%. The fourth (upper) quartile is were the probability of being above the mark is 25%.
Again, draw yourself a picture as I do in my lectures.
Yes sir but there are just 2 questions on this quartile and both of them are to find upper quartile, sir how are we going to find first, second and third quartile? For the fourth one we add it in the end with mean after being multiplied with s.d, because of being above than mean.
And for the lower (first quartile) we are going to deduct it from mean instead of adding, am i correct sir? But the second one and third one is confusing me, also third one you said is 26%
Sorry – the 26% was a typing error. It should be 25%.
Again, draw a quick normal curve. We already know that 50% of the area is below the mean and 50% is above the mean.
What you need to to calculate the values for which 25% are below and 25% are above. These, together with the mean are the quartiles.
It is exactly the same approach as in your question 2.
Sir i know all of these quartiles either 1,2 or 3 and 4 all of them would be 25%, and for 25% z score is going to be 0.67, but like for 3rd quarter that is upper quarter and in that we added it with mean, for 1st quarter we are going to deduct it from the mean right sir? But im confused about 2nd and 4th, if you can maybe provide examples for every quartile I’ll perceive it, please sir :’)
I’ll provide an example of what is confusing me
Like there is mean of 100, and question asks value of above 110 we are going to deduct from 0.5 because value is above mean but if it asks below 110 only than we add it with 0.5,
If asks between 80-110 we find probabilities of both and add them, but here I’m getting confused as in 3rd quarter it says above mean why are we adding 0.67 with mean? Lower quarter i get it because we know both areas are 50% and in first quarter it’s below 50 which is 25 so we deduct it from mean, but 2nd quarter again is confusing me same for 4th quarter that is 100%
Sir i figured it out correct me if I’m wrong, sir is 2nd quartile the middle one is known as interquartile range?
However if it’s asked to calculate median quartile, first we are going to calc lower one and upper one, and then difference of both will show us the 50% of data am i correct sir? And if it asks for 4th quartile which is 100% we are going to add both quartile value 3rd and 1st one 75 and 25% am i right sir?
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