This chapter is from the book
This chapter is from the book
This chapter is from the book
1.6 Sample Selection Methods
Proper sampling can be done either with or without replacement of the items being selected.
Sampling with Replacement
CONCEPT A sampling method in which each selected item is returned to the frame from which it was selected so that it has the same probability of being selected again.
EXAMPLE Selecting items from a fishbowl and returning each item to it after the selection is made.
Sampling Without Replacement
CONCEPT A sampling method in which each selected item is not returned to the frame from which it was selected. Using this technique, an item can be selected no more than one time.
EXAMPLES Selecting numbers in state lottery games, selecting cards from a deck of cards during games of chance such as blackjack or poker.
INTERPRETATION Sampling without replacement means that an item can be selected no more than one time. You should choose sampling without replacement instead of sampling with replacement because statisticians generally consider the former to produce more desirable samples.
Calculator Keys: Entering Data
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You enter the data values of a variable into one of six predefined list variables: L1 through L6. Your method of data entry varies, depending on the number of values to enter and personal preferences.
For small sets of values, you enter the values separated by commas as follows:
- Press [2nd][(] and then type the values separated by commas. If your list is longer than the width of the screen, the list wraps to the next line like so:
- Press [2nd][)][STO▸] and then type the variable name and press [ENTER].
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To store the values in variable L1, press [2nd][)][STO▸] then [2nd][1][Enter]. ([2nd][1] types L1, [2nd][2] types L2, and so forth.) Your calculator displays the variable name and one line’s worth of values, separated by spaces, followed by an ellipsis if the entire list of values cannot be shown on one line.
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For larger sets of data values, consider using an editor. For a calculator not connected to a computer, use the calculator’s statistical list editor:
- Press [STAT].
- Select 1:Edit and press [ENTER].
- In the editor’s six-column table (one column for each list variable), use the cursor keys to move through the table and make entries. End every entry by pressing [ENTER].
- When you are finished, press [2nd][MODE] to quit the editor.
While you are in the editor, you can move back in the column and make changes to a previously entered value. If you need to erase all the values of a column (to reuse a list variable), move the cursor to the name of the list variable (at the top of its column) and press [CLEAR][ENTER].
If your calculator is connected to a computer, you can use the TI DataEditor component of the TI Connect program (see Section A.C4). To enter a list using the DataEditor, open TI Connect, click the TI DataEditor icon, and in the DataEditor window:
- Select File → New → List.
- Select File → Properties and specify your calculator type and the (list) variable name in the Variable Properties dialog box.
- Enter the data values in the spreadsheet-like column.
- When you are finished, click the Send File icon to transfer the variable data to your calculator.
The following illustrations show the calculator’s statistical list editor and the DataEditor window, respectively, after all the values of the earlier example have been entered.
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Spreadsheet Solution: Entering Data
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Enter the data values of a variable in a blank column of a worksheet. Use the row 1 cell for the variable name.
To create a new file (workbook) for your entries, do the following:
- In Microsoft Excel versions 2007 or later, click the
Office Button, select New, and in the New Workbook dialog box, double-click the Blank Workbook icon.
- In earlier Excel versions, select File → New and select Blank workbook from a New Workbook task pane, or select the Workbook icon if the New dialog box appears.
- In OpenOffice.org Calc 3, select File → New → Spreadsheet.
To save your work, select Office Button → Save As in Excel 2007 or later. Select File → Save As in earlier Excel versions and OpenOffice.org Calc 3.
In this book, consecutive menu selections in spreadsheet programs are shown linked with this symbol: q. When you read a phrase such as File → Save As, you should interpret the phrase as “select File from the menu list near the top of the spreadsheet window and then select Save As from the drop-down menu that appears.”
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