Find the mean and standard deviation of a data set

For these five values, look for these rows:

Check the mean: $(1+2+3+4+5)/5=3$. The squared differences from $3$ add up to $10$. Population standard deviation divides this sum by $n$ before taking the square root; sample standard deviation divides by $n-1$:

These give the decimals shown above. Use the row named in your question; the list supplies both.

When a value occurs several times, enter it once with its count. Start with an empty 1-Variable table (if the numbers $1$ to $5$ are still there, clear them first, as described in the last section) and enter the marks below in x, pressing the equals key after each. Tap Stat on the function bar under the screen → Frequency and turn it On (if it already reads On, leave it). This keeps the marks and adds Freq filled with $1$; tap its first cell and enter the counts below, pressing the equals key after each. Then press the equals key on the empty row and choose 1-Var Results.

The results list shows $\bar{x}=6.4$, ${\sigma }_x=0.916515139$ (population) and $s_x=0.9660917831$ (sample). Here $f$ is a count, so $n=\sum f=10$ is the sum of the counts. Check by hand: $\sum xf=64$ and $\sum x^{2}f=418$, giving $\bar{x}=64/10=6.4$, ${\sigma }_x=\sqrt{418/10-6.4^2}\approx 0.917$ and $s_x=\sqrt{(418-10\cdot 6.4^2)/9}\approx 0.966$.

• Old numbers are still in the table: data remains when you leave or reload. Tap the trash button on the function bar under the screen, then confirm with the red Delete All button. The dialog warns that this cannot be undone; Cancel keeps the data.
• A number needs correcting: use the top-left arrow on the results list to return to the editor. Tap the wrong cell, type the correct number and press the equals key.
• A cell shows Syntax ERROR: a typo such as 1.5.5 leaves the text in the cell. Press AC to dismiss the error, then correct the entry.