A density curve is a smooth curve drawn over a histogram that represents a probability distribution, with an area of 1. It can take different shapes like a normal bell curve or a uniform rectangle. A normal distribution is a bell-shaped density curve where we can use z-scores to determine population properties or the percentile rank of a data point. If data fits a normal distribution, the 68-95-99.7 rule applies, meaning 68%, 95%, and 99.7% of data falls within 1, 2, and 3 standard deviations of the mean, respectively.
