http://www.ck12.org Chapter 4. Probability Distributions
What Joanne’s data does tell us is that the mean score (105.7) is at the center of the distribution, and the data from
all of the other scores (times) are spread from that mean. You will be learning much more about standard normal
distributions in a later Concept. But for now, remember the 2 key points about a standard normal distribution. The
first key point is that the data represented is continuous. The second key point is that the data is centered at the mean
and is symmetrically distributed on either side of that mean.
Practice
- The following data was collected on a recent 25-point math quiz. Does the data represent a normal distribu-
tion? Can you determine anything from the data?
20 17 22 23 25
14 15 14 17 9
18 2 11 18 19
14 21 19 20 18
16 13 14 10 12- A recent blockbuster movie was rated PG, with an additional violence warning. The manager of a movie
theater did a survey of moviegoers to see what ages were attending the movie in an attempt to see if people
were adhering to the warnings. Is his data normally distributed? Do moviegoers at the theater regularly adhere
to warnings?
17 9 20 27 16
15 14 24 19 14
19 7 21 18 12
5 10 15 23 14
17 13 13 12 14- The heights of coniferous trees were measured in a local park in a regular inspection. Is the data normally
distributed? Are there areas of the park that seem to be in danger? The measurements are all in feet.