What is the sample mean for the data?
The sample mean of the last 10 data points is
It is unclear from the wording of the question, but since the second data set contains only 10 data points out of a possible 24, I am assuming these 10 members is what we're calling our "sample".
Under this assumption, the sample mean for these 10 data is
#barx = (8+8+8.5+8+9+8+9+9+8.5+8)/10#
#color(white)barx = 84/10#
#color(white)barx = 8.4#
While these 10 members are a sample from a population, they are not a sample from the first set of 24 data points. This is because the second set of measurements was taken on a different night, and so the hours of sleep for each member might have changed.
If we treat the
#barx = (8+8.5+8+7.5+...+9 + 8.5 + 8)/34#
#color(white)barx = 275.5/34#
#color(white)barx ~~ 8.10#
It all depends on which population we're trying to estimate the mean from.