I purchased a set of Winnipeg Tarot Co. cards from the Winnipeg Arts Council. Here’s a sample of the artwork. More info at the Winnipeg Tarot. Co. web site.

The Simple Random Sample Generator script (SRSG) and its source code at the time of this writing can be found here. It is implemented in JavaScript and runs entirely within any modern web browser. No web servers, databases, installations, or configurations are required.

The random sampling process used within the script is based on the description given in Gay, Mills, and Airasian (2009). I adapted the directions given in chapter 5 under “Selecting a Sample,” pages 126-127.

Example usage

To explain how the script works, let’s use an example of a list of email addresses. The first steps are to generate a list of all the available email addresses of the desired population. This list can be in the form of a text file with each record on a separate line, or it can be exported as a CSV file from a program such as Microsoft Excel or from OpenOffice.org Calc. The researcher would then have to copy and paste the list into the left text area in SRSG. By default, SRSG will generate a random subset of 400 items, but this can be manually changed to a suggested maximum of 10,000. Once the researcher has placed the original list into SRSG, he or she would click the Randomize button to generate the subset. The subset is then displayed in the right text area. The results are random, de-duplicated, and unsorted. The result can then be copied and pasted back into the desired program.

Internal process

First, the script generates a pseudo-random number (a seed) using the random number generator of the JavaScript language. This pseudo-random seed is the equivalent of a blind selection of a random number from a traditional, printed random number table. This pseudo-random seed is in the range of 0 to 199,999, representing all the five-digit numbers in the random number table included in SRSG. SRSG selects the five-digit number it finds at the location found by the pseudo-random seed within the random number table. For example, if the pseudo-random number is 121065, the script will jump to that position and select 27335 as the random number.

Next, the script places the input records into an numbered array. The script counts the total number of records in order to determine the number of digits it will require for matching from the random number table. So, if in our example the count of original records is 2,000, the script will use the last four digits of random numbers it pulls from the random number table.

The script then uses the uses the first random number it finds to identify the item from the input records. In this example, the random number found was 27335. Because our original input has a total count with four digits (ie, a total count of 2,000), the script will use the last four digits of the random number, in this case 7335. It will try to find item 7335 in the input list but since the list only has 2,000 items, the script abandons the current random number and tries the next one in the random number table, 73665. The last four digits of this next random number also exceeds the total count of input records, so this random number is abandoned and the next random number is chosen. This will continue until a suitable random number is found. In our example, that random number would be 61085, the last four digits of which are 1085. This will take record 1085 out of the input data set and place it into the output data set. Once this is done, the next random number is chosen and the process repeats itself until the required number of items are placed into the output data set. If the end of the random number table is reached, the pointer jumps to the start of the random number table and continues from there.

Because the input array is indexed without leading zeros, the script will strip any leading zeros from random numbers it finds. This is mechanically different than the process described in Gay, Mills, and Airasian’s process, but it has the identical functional effect. In our 2,000 item example, Gay, Mills, and Airasian would take item number, say, 456 and pad it with a leading zero to make it 0456. If the random number 60456 is chosen, their process would take the last four digits, 0456, and match it to the item I just described.

In SRSG, the same item number, 456, would not be padded with an additional zero. When the same random number is chosen, 60456, the script first takes the last four digits, 0456, then it identifies the leading zero and strips it off, leaving 456. This approach was implemented primarily because of the way the JavaScript language stores and indexes data internally.

Once the output data set is complete, the array is formatted for output and displayed in the right text area.

Report

As soon as the results are generated, a report will be displayed in a pop-up window. The purpose of this report is to confirm and document the use of the random sampling script along with some means to verify the results without divulging any confidential information that might exist in the input or output data sets. The report will indicate the number of original input records and output records. For both the input and output records, a one-way SHA-256 hash is generated. If verification is needed that a certain input or output was processed using the SRSG script, a SHA-256 hash could be generated from the input or output data which can then be matched to the documented hash. Also in the report will be the pseudo-random seed and the first random number selected based on the seed. The report will also indicate the web browser used.

Some technical details

The random number table used in SRSG was created by RAND Corporation and is available here. This random number table has 200,000 sets of 5-digit numbers, for a total of 1 million digits. RAND Corporation provides documentation that explains how the random numbers were generated and validated.

The SHA-256 one-way hash implementation in JavaScript was developed by Chris Veness and is available here.

The SRSG script was tested in Firefox and Safari in Mac OS X. A set of 100,000 records took a minute or two to process on a 2.2 GHz CPU, 2 GB RAM laptop. At 200,000 records, the web browser seemed to stall. The script was written and tested primarily to create an output of 400 records. Very large output sets may reveal shortcomings in the script, so are not recommended. The intent of this script was to allow the researcher to create relatively smaller data sets from relatively larger ones.

References

Gay, L. R., Mills, G. E., & Airasian, P. W. (2009). Educational research: Competencies for analysis and applications (9th ed.). Upper Saddle River, New Jersey: Prentice Hall.

I’ve written about Zotero’s OpenURL resolver feature before, in which I described how to set a resolver for Central Michigan University. The same procedure can be used for many other library collections using OpenURL links listed here.

For the purposes of my own research, I have access to four research resources — my employer’s library, my municipal public library, the library of the university through which I’m pursuing current studies, and Google Scholar. By using the resources at my disposal, I’m quickly able to fill in any literature gaps that I might have before resorting to document delivery or printing from microforms.

It doesn’t appear that the capability to add multiple resolvers will be implemented into Zotero anytime soon. Changing my Zotero preferences every time I wanted to change library searches was becoming tedious. To solve this problem I’ve programmed a script that acts as an intermediate resolver. This script converts a single Zotero resolver request into links for requests to several libraries — a Zotero multi-resolver (ZMR).

A demonstration of ZMR can be found here.

At the time of this writing, ZMR is in very rough form — it doesn’t allow customization and only has links to ten library/research collections: Central Michigan University, Google Scholar, OCLC Registry, Open University, Red River College Library, Simon Fraser University, U. S. National Institutes of Health, University of Alberta, University of Manitoba, and Winnipeg Public Library. My plans are to add the available OpenURL resolvers and to allow cookie-based configuration for selecting and saving preferred resolvers.

To use ZMR in its current form, simply use the following URL as your OpenURL resolver in the Zotero preferences — http://www.kinasevych.ca/c/200912/06/multiresolver/.

To configure the printer, it must be placed in off-line mode. With the printer powered up, press the “On Line” key on its control panel to toggle between on-line and off-line modes. The printer is off-line when the light on the “On Line” button is off.

With the JetDirect card installed, the printer control panel should have a menu item named “AUX IO MENU.” Press the “Menu” key until this menu item appears in the printer display, above the control panel.

Next, press the “Item” key. The text “CFG NETWORK=NO *” should appear in the printer display. Press the “+” key, then the “Enter” key. The display should now read “CFG NETWORK=YES *”.

Press the “Item” key until the display shows “CFG TCP/IP=NO *”. Press the “+” key, then the “Enter” key to confirm the change. The text in the display should now read “CFG TCP/IP=YES *”.

To change the IP address for the printer, press the “Item” key until the text “IP BYTE 1″ text appears in the display. Press the “+” key until the desired value for the first IP byte is displayed, then the “Enter” key to confirm the change. Press the “Item” key to display the selection for “IP BYTE 2″ in the display. Press the “+” key until the desired value for the second IP byte is displayed, then the “Enter” key to confirm the change. Repeat these steps for the third and fourth IP bytes.

After the fourth IP byte is set, press the “Item” key to display the remaining network settings in the display. To change each, press the “+” key to change the value, then the “Enter” key accept the change. Press the “Item” key to proceed to the next setting.

Once the settings have been changed, press the “On Line” key to bring the printer back on-line.

The following illustrates the menu hierarchy for the AUX IO menu.

• CFG NETWORK
  • NETWORK TCP/IP
  • CFG TCP/IP
    • BOOTP
    • IP BYTE 1
    • IP BYTE 2
    • IP BYTE 3
    • IP BYTE 4
    • SM BYTE 1
    • SM BYTE 2
    • SM BYTE 3
    • SM BYTE 4
    • LG BYTE 1
    • LG BYTE 2
    • LG BYTE 3
    • LG BYTE 4
    • GW BYTE 1
    • GW BYTE 2
    • GW BYTE 3
    • GW BYTE 4
    • TIMEOUT

Printing a test page

Printing a test page before and after any changes are made helps to confirm the correct configuration of the printer. To print a test page, click the “On Line” key to place the printer into off-line mode, then press the “Menu” key until “TEST MENU” appears in the display. Press “Item” key to change the display to “SELF TEST”. Finally, press the “Enter” key. A test page should print after about twenty seconds.

Restoring user data to a new computer

But, I’ll begin these notes at the restore. The loaner laptop had a basic administrative account into which I logged in. To get started, I used Migration Assistant to prompt the OS to use my Time Machine backups as the source of the data I wished to restore. Migration Assistant correctly identified the Time Machine volume (an external Maxtor drive connected via Firewire) and the backup I wished to use. It asked which user I wished to restore, as well as whether I wished to restore previous applications. It also asked if I wished to restore network, time zone, and other configuration preferences. I took what I was offered and I accepted all available backup items. Once I completed these selections, I let Migration Assistant proceed with the restore. The remaining activity of Migration Assistant was unattended. After about 45 minutes, the restore was complete.

On completion of the restore, the loaner laptop had a new account — the identical account I had had on the original laptop. I was able to log in with the user name and password that I had previously used. Once at the Desktop, I found that all items and almost all settings from the expired laptop had been transferred to this new machine. Very, very nice.

There were some small differences worth noting. None of the printers were restored. The International icon on the menu bar, used for selecting the keyboard layout, was reset to the U.S. keyboard and none of my alternate keyboards were available. Thunderbird was acting very strangely the first two times I launched it (in one instance did not display a listing of messages but a list of the folders in the mail account), but was back to normal on the third try.

On resuming backups from where Time Machine had left off

One difference was particularly tricky to fix. Apparently, Time Machine backups rely on the MAC address of the computer to identify the hardware from which it is performing a backup. That means that when I tried to perform a backup from the new laptop, Time Machine would try to do a full backup instead of an incremental backup from where I had left off. As far as Time Machine was concerned, this was a new machine. Indeed, it was. But I wanted it to be treated like the old laptop, as though there were no interruption.

To convince Time Machine to treat the new laptop as though it were the new one, I followed the instructions I found here at the Mac OS X Hints web site. The following summarizes the procedures I followed.

First, I disabled Time Machine by clicking its prominent On/Off button.

Using System Profiler, under Network > Ethernet, I located and noted down the MAC address of the new computer. Next, I noted down the name of the external Time Machine volume and of the computer I wished to backup. Also, I noted down the MAC address used by the original computer using a command issued in Terminal. For this last part, I used the following commands in Terminal.

cd /Volumes/BACKUPVOLUME/Backups.backupdb
xattr -p com.apple.backupd.BackupMachineAddress COMPUTERNAME

I used the name of the Time Machine backup volume for BACKUPVOLUME, and the name of my computer for COMPUTERNAME.

Next, I issued the following series of commands in Terminal.

sudo fsaclctl -p /Volumes/BACKUPVOLUME -d
cd /Volumes/BACKUPVOLUME
sudo mv .a0a1a2a3a4a5 .b0b1b2b3b4b5
sudo xattr -w com.apple.backupd.BackupMachineAddress NEWMACADDRESS Backups.backupdb/ COMPUTERNAME
sudo fsaclctl -p /Volumes/BACKUPVOLUME -e

For .a0a1a2a3a4a5, I used the old MAC address without the colons but with a preceding period. A MAC address a0:a1:a2:a3:a4:a5 would therefore be keyed as .a0a1a2a3a4a5. For .b0b1b2b3b4b5, I used the new MAC address without the colons but with a preceding period, in the same manner as for the old MAC address, already described.

For NEWMACADDRESS, I used the MAC address of my computer, with colons.

Once these steps had been completed, I remounted the backup volumes (ejected them, then reconnected them), restarted Time Machine (big On/Off button back to the On position), and selected the desired backup volume in Time Machine using the Change Disk button.

The next backup that was done took a while, but it was an incremental backup simply restoring its various links.