The SAMPLE MEAN is the mean of a sample.

The POPULATION MEAN is the mean of the population.

Different symbols make the distinction between these two, although the formulas are exactly the same.

**The ONLY difference between the two is that the SAMPLE MEAN is referred to as "x bar" whereas the POPULATION MEAN is referred to as "mew." BOTH are found by calculating the SUM of all values you are given and dividing by "N," the number of total values. **

We can often use x bar, the SAMPLE MEAN, to draw conclusions about the mean of the entire population.

Disclaimer: I did not create nor do I own these videos. I have simply embedded them, courtesy of YouTube.

Notice this:

**The SAMPLE MEAN and the POPULATION MEAN are found using exactly the same formula. **

**The ONLY difference between the two is that the SAMPLE MEAN is referred to as "x bar" whereas the POPULATION MEAN is referred to as "mew." BOTH are found by calculating the SUM of all values you are given and dividing by "N," the number of values you are given. **

"Variance" seems like a term unrelated to standard deviation, but in fact - the variance is just the SD^2 (Standard Deviation, Squared).

The reverse is therefore true. The Standard Deviation is the SQUARE ROOT of the variance.

;

Disclaimer: I did not create nor do I own these videos. I have simply embedded them, courtesy of YouTube.

Disclaimer: I did not create nor do I own these videos. I have simply embedded them, courtesy of YouTube.

Command: invNorm(.75,46,2.7)

The Standard Deviation is the SQUARE ROOT of the VARIANCE.

The official formula for the POPULATION Standard Deviation is:

It is very important that you understand what a Z-score represents as well as how to obtain a Z-score manually, by hand.

HOWEVER, you should also know how to get around your TI-83 or 84 series calculator. Use it to find a Z-Score and the AREA under a curve.

And here is another, more comprehensive overview of Z-Scores: