normal distribution

[khalil]

Need help please

The weight of cats is evenly distributed. It is known that 10% of cats weigh more than 1.8kg, and 15%of cats weigh less than 1.35kg. Find the mean and s.d of this distribution

[kamil9876]

Drawing a normal distribution curve, you can see that the mean, which I will denote as M, is in between 1.8 and 1.35. I will call d the standard distribution.



90% of cats wiegh weight less than 1.8kg. Hence find the z value that corresponds to 90%, call this :

  (1)

15% of cats wiegh less than 1.35. Find the z value that corresponts to 15%, call this :

   (2)


Notice taht once you find and you have an equation with two unkowns to solve for (M and d). Hence you should be able to find these values.

[khalil]

Do you mean to make z1=z2 and solve? I did that and got a false solution. What do i do with tthe percentages?

[kamil9876]

no you do not do that. The z1 and z2 are determined by the percentages, because the percentages (probabilities really) are different the z1 adn z2 msut be different.

I don't know how you kids are taught to do it but basically it's solving for a z1 and z2 such that Pr(z<z1)=0.9. Pr(z<z1)=0.15. (There's a table that can convert this for you but I'm guessing that with fancy calculators you can do this much simpler).

I hope someone here can help on this one because I forgot how to use the technology as I only concern myself with pure mathematics these days.

[khalil]

kids? how old are you?

[kamil9876]

kids? how old are you?

Not much older, was just referring to how year 12 feels like ages away and a completely different world(especially when it comes to using graphics calculator and trivial information).

[TrueTears]

kamil9876 is a grown up man and is already supporting a family of 5.

As for the question, Z1 and Z2 like kamil said are determined by the %, you need to equate the values you have on your normal distribution curve with the values that produce the same area from the STANDARD normal distribution curve. The inverse normal function in stats list editor can do this.

[khalil]

kamil9876 is a grown up man and is already supporting a family of 5.

As for the question, Z1 and Z2 like kamil said are determined by the %, you need to equate the values you have on your normal distribution curve with the values that produce the same area from the STANDARD normal distribution curve. The inverse normal function in stats list editor can do this.

WOH WOH. wait a second. Before kamil changed his pic, wasnt it a girl before? I remember vividly. It was of these two girls and had caption 'me n my friend'

[TonyHem]

kamil9876 is a grown up man and is already supporting a family of 5.

As for the question, Z1 and Z2 like kamil said are determined by the %, you need to equate the values you have on your normal distribution curve with the values that produce the same area from the STANDARD normal distribution curve. The inverse normal function in stats list editor can do this.

WOW WOW. wait a second. Before kamil changed his pic, wasnt it a girl before? I remember vividly. It was of these two girls and had caption 'me n my friend'

rofl

[khalil]

Also, can I just add, if TT is, in fact, a girl, then why, on Kamil's signiture, does it say that 'HIS thirst for karma increases exponentially'?

I probably sound like an investigator, and I couldnt care less if you were a boy or girl, but i'm just intrigued

[kurrymuncher]

*facepalm*

[TrueTears]

Dude ofcourse I'm a girl, after all I do go to Scotch, an all girl's school

[khalil]

Girls don't say dude

[kamil9876]

Girls don't say dude

Maybe in certain kinds of movies they don't, but exposure to them in reality may reveal otherwise.

[kurrymuncher]

Girls don't say dude

Maybe in certain kinds of movies they don't, but exposure to them in reality may reveal otherwise.

quote of the century!!!!!!!!!!!