Question

Decide if the function shown in the figure below is a probability density function (pdf) or a cumulative distribution function (cdf). Let A = 4.
This function is a
cumulative distribution function or probability density function? PLease explain to me why

Find the exact value of c. Please explain how you found c.

Attachement below

Answer 1

I need a calc genius!!

Answer 2

It's continuing to increase up to some maximum value, so it looks like probabilities are accumulating.
For either cdf or pdf, the area under the curve =1, so you can use that and the geometry of the graph to find Ac and c.

Answer 3

I hope I'm interpreting this right. . .

Answer 4

How did you determine that the area was 1. And how geometrically

Answer 5

Sorry. Correction, for a cumulative function, the maximum value is 1.
This means that A∙c=1, and since A=4, c=1/4.

Answer 6

I guess im still confused. How can it be both a cdp and pdf?

Answer 7

It is not both. It is cpd

Answer 8

If pdf then the area under the curve =1, but this is cumulative so the max. value =1.

Answer 9

ah. How did you determine it was a cdf? Sorry pleas bare with me

Answer 10

From the shape of it. The probabilities are increasing as it goes and maxes out in a flat line that continues indefinitely. If it were a pdf, then at some point, the curve would have to come back down to zero.

Answer 11

oh my mistaske got it! thank you very much wish you were my calc teacher

Answer 12

If you have more probability/stats-like questions, try this site. It is very easy to read:

http://stattrek.com/probability-distributions/probability-distribution.aspx?Tutorial=Stat

Answer 13

Thanks cliffsedge

Answer 14

You're welcome.

Answer 15

Oh, for cdf what would c be? (Its regarding another problem)- Does its also tend to 1?

Answer 16

I now know its pdf(thanks to you)

Answer 17

got it :)

Answer 18

Is A still 4 in this case?

Answer 19

I got it ;) it was 3. Im i right in the fact that i set the area under the curve to that of a triangle egual to 1?

Answer 20

Yes, if A=3, then area = 1= 0.5(3)(c).

Answer 21

cool whip

Answer 22

Indeed. \[\large \ddot \smile\]