### PDF

Given a probability density function find the mean, median and mode of the distribution.

### Scale Invariance

By exploring the concept of scale invariance, find the probability that a random piece of real data begins with a 1.

### Into the Exponential Distribution

Get into the exponential distribution through an exploration of its pdf.

# Exponential Intersection

##### Age 16 to 18 Challenge Level:

The pdf $f(x)$ of an exponential distribution with parameter $\lambda$ is
$$f(x) = \lambda \exp(-\lambda x)\quad x\geq 0$$
The cdf $F(x)$ of such a distribution is
$$F(x) = \int^x_0 f(x') dx'$$

Use your analytical skills to answer these questions:

1. Must the pdfs of two different exponential distributions intersect?
2. In what cases do $F(x)$ and $f(x)$ intersect?
3. Can the cdfs for two exponential distributions intersect?
4. Can the pdfs for three different exponential distibutions intersect at the same point?

You might want to experiment with specific choices of $\lambda$ before constructing more general arguments.