Distributions

Normal

Normal distributions are commonly found "in nature," including in marketing research, so they're worth mentioning. This distribution is sometimes called a "bell curve" because of the nifty shape it makes in a histogram.¹

The basic shape of a normal distribution is a grouping around the mean, with observations more and more distant from the mean getting less and less likely.

The histogram at the bottom of the page shows an approximately normal distribution in response to a survey question: "Overall, what is your evaluation of the ad?" that had a response scale of 1 to 7.

Please note these distributions are not "normal" in the sense that all distributions "should" take this form. That is, if you see a distribution that's severely non-normal (e.g., it is strongly skewed), that's not "bad" in any normative sense.

There are a variety of complex mathematical properties to the normal distribution that we will not pursue in this class. But take my word for it: normal distributions are super cool.