Using the TI-84 to Calculate Standard Deviation | Step by Step Guide

Understanding standard deviation is essential in both statistics and everyday data analysis. It tells you how spread out your data is around the mean (average). Instead of solving it by hand, you can use the TI-84 calculator to calculate standard deviation in seconds.

In this guide, you’ll learn how to calculate standard deviation using the TI 84, step by step, with examples for both sample and population data.

What Is Standard Deviation?

Standard deviation shows how much variation there is from the average. A low standard deviation means data points are close to the mean, while a high standard deviation means they are spread out.

There are two types:

• Sample standard deviation (Sx): For a subset of data.
• Population standard deviation (σx): For all members of a data set.

How to Enter Data into the TI-84

Before calculating standard deviation, enter your data into a list.

Example Data:

12, 15, 18, 22, 25

Steps to Enter Data:

1. Press STAT
2. Press ENTER to select Edit
3. Go to L1 and type your numbers one by one, pressing ENTER after each

How to Find Standard Deviation on TI-84 Once your data is in L1, follow these steps:

Step by Step Instructions:

1. Press STAT
2. Arrow right to CALC
3. Choose 1-Var Stats and press ENTER
4. It will ask: 1-Var Stats L1
   • If not shown, press 2nd then 1 to insert L1
5. Press ENTER

Output Explanation:

You’ll see results like this:

• x̄ = mean (average)
• Σx = sum of values
• Sx = sample standard deviation
• σx = population standard deviation
• n = number of data points

Which One to Use: Sx or σx?

• Use Sx if you are working with a sample from a larger population (common in statistics problems)
• Use σx if your data represents the entire population

Example:

For the data 12, 15, 18, 22, 25, your calculator might show:

• Sx ≈ 5.02
• σx ≈ 4.48

Clear or Edit Your List

If you want to calculate again with new data:

To clear L1:

1. Go to STAT → Edit
2. Arrow up to L1 until it’s highlighted
3. Press CLEAR, then ENTER

Now L1 is empty and ready for new data.

Quick Tips

• Always check your list for errors before running the stats
• Use ZoomStat (ZOOM → 9) if graphing data after stats
• Use 2nd + number keys (L1, L2, etc.) to select lists quickly

Common Questions

Can I use the TI 84 Plus CE for this?

Yes. The steps are the same on TI 84 Plus, TI 84 Plus Silver Edition, and TI 84 Plus CE.

What if I want standard deviation for grouped data?

Use the frequency list option. Example:

• Data in L1
• Frequencies in L2
• Run: 1-Var Stats L1, L2

Conclusion

The TI-84 calculator makes it simple to calculate standard deviation for both sample and population data. Whether you’re in a statistics class, taking the SAT, or just analyzing numbers, this tool saves time and improves accuracy.

Practice with different data sets so you’re confident on tests or homework assignments.