Answer: 74 inches
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Explanation:
The given stem and leaf plot leads to this data set
68,68,69,69
71,72,77,77,78,78
80,81
I broke it up to have each tens digit get its own row. That way it's bit more readable.
Unfortunately, the term "average" in math is very vague. It could mean one of the following
To get the mean (specifically the arithmetic mean), we will add up the values and then divide by n = 12 because there are 12 values in the list above. Adding said values gets us
68+68+69+69+71+72+77+77+78+78+80+81 = 888
Dividing that over 12 then leads to 888/12 = 74
The arithmetic mean is 74.
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To get the median, we would first sort the data set. Though that is already done for us. From here, we locate the middle-most item.
Since there are n = 12 items here, the middle item is between slot n/2 = 12/2 = 6 and slot 7
The values in slots 6 and 7 are 72 and 77 respectively. The midpoint of those values is (72+77)/2 = 149/2 = 74.5
The median is 74.5
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The mode is possibly the quickest measure of center or average we can compute. We simply look at the value that shows up the most. In this case, the following values show up twice (which is the most frequent of all the values)
They are all tied for the title of "mode". It's possible to have more than one mode, so we say the mode is the set {68,69,77,78}.
Due to the nature of multiple modes, the mode is often not a good measure of center (but it's still a possibility; especially for categorical data).
In this case, I think the mean or median is a better measure of center.
Since there aren't any outliers, the mean is the best measure of center in this case. Luckily, the mean and median (74 and 74.5 respectively) are fairly close to one another.
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To summarize everything, the term "average" is too vague and it could refer to the mean, median or mode. In this problem, the mean is possibly the best measure of center since there aren't any outliers and the mode isn't one single value.
We found the following:
- mean = 74
- median = 74.5
- mode = {68,69,77,78}
It's very likely your teacher is wanting the mean.
