Calculator Use (Leaving Cert Mathematics): Revision Notes

Calculator Use

Overview

Using a calculator to compute the standard deviation simplifies the process, especially for large data sets. Most scientific and graphing calculators have built-in functions to calculate the standard deviation. The steps below outline how to use a calculator effectively:

Steps for Different Calculators

Casio ClassWiz (fx-991EX / fx-570EX / 83/85/991 CW series)

1. Enter STAT mode Press [MODE] (or [MENU]) → choose STAT.

2. Choose 1-Var Select 1-Var (one-variable statistics).

3. Enter your data Type each number, press =. Continue until all values are entered.

4. Calculate Press [OPTN] → 1-Var (sometimes shown as Calc).

You'll see results like:

• n = number of data points
• Σx, Σx² etc.
• σx (population standard deviation)
• sx (sample standard deviation)

5. Choose the right one Exams usually want sx (sample SD).

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Casio fx-83/85GTX and fx-991ES PLUS (ES family)

1. STAT mode Press [MODE] → STAT.

2. Pick 1-Var Select the option for 1-Var.

3. Enter data Type each value, press =.

4. Show SD Press [SHIFT] [1] (STAT) → choose Var → pick:

• σx for population SD
• sx for sample SD Tip: If you only want mean and SD, you don't need to choose regression — just stick with 1-Var.

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Texas Instruments TI-84 Plus CE / TI-84 Plus / TI-83

1. Enter data [STAT] → 1

   …. Put your data in L1.

2. Run 1-Var Stats [STAT] → CALC → 1:1-Var Stats.

Then type L1 (use [2nd][1]) → ENTER.

3. Read results

• x̄ = mean
• Σx, Σx² etc.
• Sx = sample standard deviation
• σx = population standard deviation

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Casio fx-CG50 / fx-CG20 (graphing)

1. STAT mode [MENU] → STAT → Edit.

2. Enter data Type your values into List1.

3. Calculate Press [F2] CALC → [F1] 1-Var.

4. Read SD The results screen lists σx and sx (scroll if needed).

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Sharp (e.g., EL-W531/531XH/506 family)

1. STAT mode Press [MODE] → STAT.

2. Choose 1-Var Select single-variable stats.

3. Enter data Type each value (often as number → DATA key).

4. Calculate Press 2ndF → STAT (or STAT VAR depending on model).

Scroll through results until you see σx and sx.

Key Considerations

• Understand whether the data represents the entire population or a sample:
  • Use $\sigma$ for population.
  • Use $s$ for sample.
• Clear the calculator memory before entering new data to avoid errors.

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Summary

• Calculators simplify the computation of standard deviation for both small and large data sets.
• Steps:
  1. Enter the data into the calculator.
  2. Use the statistical mode and select the appropriate standard deviation function ($\sigma$ for population, $s$ for sample).
  3. Read the result.
• Always ensure you know whether the data set represents a population or a sample to choose the correct standard deviation function.