Students in a Grade 7 class measured their pulse rates. Here are their results in beats per minute. 97, 69, 83, 66, 78, 8, 55, 82, 47, 52, 67, 76, 84, 64, 72, 80, 72, 70, 69, 80, 66, 60, 72, 88, 88 1)Calculate the mean, median, mode, and range. mean = 69.8 median = 72 mode = 72 range = 89 2)Are there any numbers that are significantly different from the rest? If so, remove them and calculate the mean, median, and mode again. Different = 8 mean = 72.4 median = 72 mode = 72 range = 50 3) Explain how the averages are affected. The mean is now closer in value to the median and mode. Median and mode did not change.

1) How did you decide which numbers were significantly different? 2) Which measure of central tendency was most affected by the number that was significantly different? (mean, mode, or median) = the mean was the only measure that changed 3) Which measure(s) of central tendency are more reliable when the data contain significantly different numbers? = the median is more reliable as it is not really influenced by outliers because it is the middle number 4) Do you think “8” should be used when we report averages? 5) Why not? = no one has a pulse rate of 8 so it must be a mistake

Facts: 1)A number in a set of data that is significantly different from the other numbers. 2) An outlier is much greater or much less than most numbers in the data set. 3) Outliers occur as a result of an error in measuring or recording and should be ignored. 4) Sometimes, an outlier is an important piece of information that should not be ignored. 5) Outliers may not always be obvious.

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