My thread of questions

[khalil]

So, for my question, can the answer be both dilation from the x and y axis?

[kamil9876]

yep.



a=4 is your case.

[khalil]

The picture below shows two graphs. I started of with f'(x) and from that I needed to draw f(x). I understood where the turning points went, but how do I determine its y intercept?

[m@tty]

You can't tell the intercepts, with the gradient function only. Thus the indefinite '+c', when integrating.

[khalil]

True, but how do I know that the y int of f(x) will be postive and not negative
There must be some sort of rule to draw these graphs

[TrueTears]

True, but how do I know that the y int of f(x) will be postive and not negative
There must be some sort of rule to draw these graphs

You won't know because the +c is vertical translation.

[khalil]

Why don't I round off when finding the mean of people (click below)

[ngRISING]

MC Question. Suppose that weights of males at a health club are normally distributed. If 70% of the males weight more than 90KG, 10% weight more than 120kg, then the mean and the SD of weight in this club are equal to:

A) U = 100.4 . sd = 18.3
B) U = 111.3 . sd = 16.6
C) U = 69.2   . sd = 39.6
D) U = 110.8 . sd = 39.6
E) U = 98.7  . sd = 16.6

[TrueTears]

Let X be the random variable for the weight and Z as the standard normal variable.

Let = s.d and = mean

Pr(X > 90) = 0.7

Pr(X > 120) = 0.1

Inverse normal of 0.7 = -0.5244

Inverse normal of 0.1 = 1.28155

Thus



Solve simultaneously.

[khalil]

What about my question

[TrueTears]

What about my question

Expected value is never to be rounded. It's the 'expected' value.

It's kind of like finding the average, say you have heaps of numbers eg, 1, 4, 7, 12, 15 and you want to find the average of those, the number you get will probably not be one of those numbers, but you still take it as the "average" that is similar to expected value, the value you "expect" doesn't have to make sense with the situation.

EDIT: sailor mars too fast =(

[khalil]

What about my question

Expected value is never to be rounded. It's the 'expected' value.

It's kind of like finding the average, say you have heaps of numbers eg, 1, 4, 7, 12, 15 and you want to find the average of those, the number you get will probably not be one of those numbers, but you still take it as the "average" that is similar to expected value, the value you "expect" doesn't have to make sense with the situation.

EDIT: sailor mars too fast =(

thanks sailor moon!

[VeryCrazyEdu.]

Let X be the random variable for the weight and Z as the standard normal variable.

Let = s.d and = mean

Pr(X > 90) = 0.7

When using inverses you have to make sure all the probabilities are Pr(X<__) otherwise it won't work. The inverse always measures the area from the left. so you should inverse Pr(X<90)=.3 etc.

i dunno if this is what you meant but hope i helped

Pr(X > 120) = 0.1

Inverse normal of 0.7 = -0.5244

Inverse normal of 0.1 = 1.28155

Thus



Solve simultaneously.

[VeryCrazyEdu.]

lol sorry my reply didn't come up! haha

you have to make sure that all probabilities are in the form Pr(X<__) because inverse measures the area from the left.

[TrueTears]

lol sorry my reply didn't come up! haha

you have to make sure that all probabilities are in the form Pr(X<__) because inverse measures the area from the left.

Actually don't, from the calc it is always the upper right bound, so just take opposite sign of the answer from the calc because it's symmetrical about 0.

Forgot to mention: only use symmetrical properties if it's the normal standard you are dealing with, if it is just normal distribution, you gonna have to do some arithmetic around the mean.