4.1. Normal Distributions http://www.ck12.org
If you take a normal distribution curve and place it over Thomas’s histogram, you can see that his data also does not
represent a normal distribution.
Guided Practice
Joanne posted a problem to her friends on FaceBook. She told her friends that her grade 12 math project was to
measure the lifetimes of the batteries used in different toys. She surveyed people in her neighborhood and asked
them, on average, how many hours their typical battery lasts. Her results are shown below:
98 108 107 79 100 112 97 79 41 127
135 100 92 80 66 62 119 118 56 112
99 83 86 62 127 155 107 140 144 122
110 116 134 102 133 157 100 96 55 132
126 171 169 146 122 74 70 82 84 93
Is her data normally distributed? Where is the center of the distribution?
Answer:
If you take a normal distribution curve and place it over Joanne’s histogram, you can see that her data appears to
come from a normal distribution.
This means that the data fits a normal distribution with a mean around 105. Using the TI-84 calculator, you can
actually find the mean of this data to be 105.7.