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In ordinary terms, the sample mean is the sample average.
Question:
What is the average age of the ten given ages below:
{ 18 , 18 , 19 , 19 , 19 , 19 , 20 , 20 , 20 , 25 }
Mean of a Sample
As the title suggests the first objective is to study the middle or center of the data set. These measures that we use are also called parameters. The mean is a parameter. The mean is also a statistic. ( We often phrase these important measures as "statistical parameters".)
So it's best to begin with the famous measure: the mean of
a sample.
We employ the symbol 
for the sample mean.
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Question:
College math grades are given as :
{78 , 60 , 91 , 75 , 60 , 80 ,72 , 98 }
Find the mean grade.
sample.
This index notation represents first data point as x1, second data points as x2, third data set as x3,...
Sample Mean =
Sample Mean=
(In later chapters we will do some error analysis for sample means and do several calculations that involve
(
-
E) and ( +
E) where E is Error. )  |
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In other words the concept of mean is so simple that is often applied in our daily lives. The weather reader, for example, talks about temperatures being "above average" or "below average" for this time of year. It will take a few more chapters to better quantify and explain the sample mean as one of the most important (and easy) statistical parameters.
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