Hey,

Thank you for your question!

Following the link, you will open a desmos graph where I have defined two functions - f(x) and g(x). Let me quickly guide you through the website. By clicking on the empty circle to the left of each function, you will see it displayed on the coordinate system. You are able to display multiple graphs on the same plot. Using the scroller on your mouse, you can zoom in and out on the coordinate system.

Let me first discuss the function f(x) = x^2. The resulting graph is a parabola. Here are the coordinates of a couple of points on this parabola:
x = 1 -> f(x) = 1^2 = 1
x = 2 -> f(x) = 2^2 = 4
x = 3 -> f(x) = 3^2 = 9

Now, on the same coordinate system, let's display the function f(2x). It bears the following form:
f(2x) = (2x)^2 = 4x^2
What I did above was to replace the x from the previous example with a 2x. On the plot, you see that the resulting parabola is narrower than the first one. Here are the coordinates of a couple of points on this new parabola:
x = 1 -> f(2x) = 4*1^2 = 4*1 = 4
x = 2 -> f(2x) = 4*2^2 = 4*4 = 16
x = 3 -> f(2x) = 4*3^2 = 4*9 = 36

So, you see that for the same value of x, the y-value of the two parabolae is different. More specifically, for the same value of x, the y-value of the second parabola is higher than the y-value of the first one. This is why the second one turns out to be narrower than the first one.

Analogously, you can plot the function f(x/2) and argue for yourself why the resulting parabola is more spread out that the one of f(x).

As a second example, I have plotted the function g(x) which has the form of a normal distribution. Applying the same arguments and trying to calculate the y-values of the functions for the same values of x, try to explain why g(2x) is narrower than g(x) and why g(x/2) is more spread out :)

Hope this answer helps!

Kind regards,
365 Hristina

Resolved: transforming random variables

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