Question

will some one show me how to do this math problem?
Find the values of the 30th and 90th percentiles of the data.
129, 113, 200, 100, 105, 132, 100,176, 146, 152

Answer 1

Have you considered sorting them from low to high? You will be almost done when you have done that.

Answer 2

100, 100, 105, 113, 129,132,146,152, 176,200

Answer 3

Now, we have to agree on a definition. What does "percentile" mean?

Argue with 50%
1) Does it mean I EXCEED 50% of the data?
2) Does it mean there is 50% on one side and 50% on the other side?
3) Something else?

Answer 4

I am so confused.
where do you get the 50%?
(i don't know how to do this this is the first time I've had to do this)

Answer 5

I pulled it out of a hat for the sake of argument. What does "percentile" mean? This is what we need to know. The answer changes based on the definition. There should be examples or clear definitions in your course materials.

Answer 6

in my text book it says a percentile is a number from 0 to 100 that you can associate with the value x from a data set. it shows the percent of the data that are less than or equal to x.

Answer 7

Okay, that is good.

We have 10 items. This means that each one represents 10% of the distribution. Make sense?

Answer 8

yes

Answer 9

is the 3rd on the 30th?

Answer 10

*one

Answer 11

There is one problem to overcome in these data. "100" appears twice. That's a little annoying, but we can deal with it.

If there were only one "100", we could say "100" defines the 10-percentile.

Since there are two, we will have to say that "100" defines the 20-pecentile and there just is no 10-percentile.

Still making sense?

Answer 12

yes.

Answer 13

Now, we can define the WHOLE distribution. You are right about the 3rd one.

100 - 20-percentile
100 - 20-percentile
105 - 30-percentile
113 - 40-percentile
129 - 50-percentile
132 - 60-percentile
146 - 70-percentile
152 - 80-percentile
176 - 90-percentile
200 - 100-percentile

... and we can answer ANY question about percentiles from these data.

Answer 14

so what happens to the 10%? it just disappears ?

Answer 15

Yup. That duplication made it vanish.

Answer 16

i know its irrelevant in this problem

Answer 17

okay. thank you. but the third on is still the 30th

Answer 18

There is one important things hanging out in the examination of percentiles. The 50-percentile has a special name. Do you know it?

Answer 19

i dont

Answer 20

It is the "median". Also irrelevant to this problem, but you'll need that at some point.

Answer 21

oh. so would the median be 130.5?

Answer 22

Well, you have to change your definition of a percentile if that is the median. That is the "50 on one side and 50 on the other side" definition. Some feel that the median has to be IN the set. There is a little trickery around the whole thing. Read definitions carefully.