http://www.ck12.org Chapter 4. Probability Distributions
you can connect the points on the graph. For the second graph, the price of a gallon of gas at the end of each year
is recorded. In 1930, a gallon of gas cost 10c. You would not have gone in and paid 10. (^2) c or 9. (^75) c. The data is,
therefore, discrete, and the data points cannot be connected.
Let’s look at a few problems to show how histograms approximate normal distribution curves.
Example B
Jillian takes a survey of the heights of all of the students in her high school. There are 50 students in her school. She
prepares a histogram of her results. Is the data normally distributed?
If you take a normal distribution curve and place it over Jillian’s histogram, you can see that her data does not
represent a normal distribution.
If the histogram were actually shaped like a normal distribution, it would have a shape like the curve below:
Example C
Thomas did a survey similar to Jillian’s in his school. His high school had 100 students. Is his data normally
distributed?