normal distribution questions

[kkaman]

Hello everyone, is there anyone to help with the ND and percentile questions. I earlier posted....but no body replied. Here is the earlier post............
1) If 10,11,12 correspond to the 50,k,70 percentile, compare k and 60''.(2) ''If 350, 450 and 550 correspond to the 15, k, 45 percentile, compare kand 30''.In the first question,why K>60. The normal distribution is symmetric with more observations around the mean than those away from the mean. In this case 12 is 70th percentile means that at least 70 percent of the observations are at or below it. 11 would therefore be less than 70th percentile but how do we see that it would be greater than 60.In the second case, all the observations are below the mean with 15 percent at or below 350( about 2SD below mean) and 550 corresponds to about 1/4th of SD away from mean. how do we see that K<30.I would appreciate an elaborate reply.

[Fanatdk]

Hello everyone, is there anyone to help with the ND and percentile questions. I earlier posted....but no body replied. Here is the earlier post............
1) If 10,11,12 correspond to the 50,k,70 percentile, compare k and 60''.(2) ''If 350, 450 and 550 correspond to the 15, k, 45 percentile, compare kand 30''.In the first question,why K>60. The normal distribution is symmetric with more observations around the mean than those away from the mean. In this case 12 is 70th percentile means that at least 70 percent of the observations are at or below it. 11 would therefore be less than 70th percentile but how do we see that it would be greater than 60.In the second case, all the observations are below the mean with 15 percent at or below 350( about 2SD below mean) and 550 corresponds to about 1/4th of SD away from mean. how do we see that K<30.I would appreciate an elaborate reply.

waiting for somebody's smart response. where did you get those questions?

[pankeshlinux]

Can you Specify 10,11,12 is it percentile or a normal number ?



From
Pankesh Patel
Jai hind...

[thesanjeeva]

I never want to give my time on such long questions . God help me. May god help you as well.

[kkaman]

thesanjeeva they are not long questions rather just one line questions.
Fanatdk they are powerprep questions, if i remember correctly. that kind of stuff might appear on the real test. I'm wondering whether anyone is there to clarify the concepts, may be ask goldust or geek godess??

[Fanatdk]

thesanjeeva they are not long questions rather just one line questions.
Fanatdk they are powerprep questions, if i remember correctly. that kind of stuff might appear on the real test. I'm wondering whether anyone is there to clarify the concepts, may be ask goldust or geek godess??

now its really scary, cause I have no idea how to solve these questions If you know that it's real powerprep questions, so probably it should be explanation as well.

Plz, guys if you have any ideas, HELP US!!!!

[pankeshlinux]

pls gie clarification on these Questions

[kkaman]

'Here is the answer from Goldust'

Both your questions can be answered if you know how the normal distribution works. There are two things you should realize:-

a. The distribution is a bell-shaped curve, with the peak at the 50th percentile.

b. The percentile refers to the part of the total area that is covered from -infinity up to that point

1. In this question, all your data points are to the right of the centre. This means that the curve is more or less decreasing i.e. it has a downward slope. The values 10,11,12 are plotted on the x-axis, and they will obviously be equispaced. However, the curve itself is decreasing in value. Hence, it is logical to say that the area between 10 and 11 is greater than the area between 11 and 12. Since 10 <-> 50 percentile and 12 <-> 70 percentile, the 60th percentile should lie somewhere such that the area between 10 and the 60th percentile equals the area between the 60th percentile and 12. The situation so far can be summarized as follows:-

Area between 10 12
11 Greater Lesser
60th percentile Equal Equal

The area between 10 and 11 is greater than the area between 10 and the 60th percentile. Since 11 <-> k percentile, k > 60.

I know that the above explanation might seem very complicated, but if you understand the two rules that I stated above, it should follow quite easily.

2. Absolutely identical logic. The area between 350 and 450 is lesser than that between 450 and 550 (since the points are to the left of centre). The area between 15th and 30th percentiles is equal to the area between the 30th and 45th percentiles. Thus, the area between kth percentile and 45th percentiles is greater than the area between 30th percentile and 45th percentile. Since the points are to the left of the centre, to get a greater area, k < 30.

Try drawing the above solution on a normal distribution figure. It will make visualization easier.

[racerunner]

Thank you very much for your reply, now it's clear!