Lecture notes‎ > ‎

## For today you should have:

2. Prepare for a quiz on Chapters 1-5.
3. Midpoint survey.

## Today:

1. Quiz.
2. Survey.
3. Project suggestions.
4. Convolution.
5. Homework 6 preview.

1. Homework 6.

### Survey results

Generally positive, so that's good.

Time spent: a little low.

Bad things: not enough time for project, not enough structure for project, more help with probability.

NINJAs: generally positive, some questions about homework feedback.

### Project suggestions

1) Look at the next deadline and work backward.  Where should you be?

2) Allocate 2 hours per week and schedule it.

3) Look at distributions and choose summary statistics.

Counterexample: mean doubling time.

4) Look at scatterplots and identify relationships.

5) Design other visualizations.

Warning: don't call something a {PMF, CDF, scatterplot} unless it is a {PMF, CDF, scatterplot}.

For example, suppose I compute the probability of early birth as a function of mother's age.  It maps from age to probability, but it is not a PMF.

Suppose I compute average pregnancy length as a function of mother's age.  It shows one variable versus another, but it is not a scatterplot.

Identify apparent effects now; soon we will learn:

1) Test whether an apparent effect might be due to chance.

2) Estimate the size of the effect.

3) Quantify relationships.

### Convolution

Operations on distributions tend to be easy to implement numerically, a little more challenging to do analytically.  For example, here is the CDF of Z =  X + Y: