Using Computers for storing and retrieving MR Data

Entering data into the Computer: After the editor has reviewed the individual responses to all questions and has assigned a numerical code to each response, those coeds will be available when the data on the completed questionnaires are to be entered into the computer. This is accomplished by transferring the coeds into computer memory space or onto computer tapes or cards in preparation for computer tabulation. Virtually all studies and certainly all large studies are now computer-tabulated. Computers are used because (1) it is faster to tabulate by computer than manually, (2) it is more economical than tabulating by hand, (3) computer tabulation are more accurate than hand tabulations and (4) computers are absolutely necessary when sophisticated calculations and tabulations are to be made. Because of these advantages, the following discussions will be concerned with computer tabulation rather with manual tabulation.

Computer Memory Space:

Readers can think of computer memory space as a sheet of paper with a number of rows and a number of columns. Data are stored in the rows and columns in some organized manner. Typically, one row of space is assigned to the data from each questionnaire. There will be at least 80 columns and often 200 or more columns available for storing data. One or more of the columns should be reserved for each question on the questionnaire, and this column reservation scheme should be identical for all questionnaires.

After the responses to each question on a questionnaire have been coded, the codes are entered into their appropriate columns. Typically this is accomplished by either a typing or a key punching operation quite similar to a person’s typing the coded numbers in rows and columns on a sheet of paper.

Example: An automobile driving survey includes a dichotomous question (Do you have a valid driver’s license?): a multiple choice question (Is the car you drive most frequently American made, European made, or Japanese made?); and an open question (How many thousands of miles did you drive your automobile last year?). Researchers wished to record the exact answers to the last question, to the nearest thousand miles.

Answers to the first two of these questions are to be recorded in columns 20 and 40, respectively of computer memory space, while answers to the third question are to recorded in columns 60 and 61. If the first respondent answered “Yes” to the driver’s license question, a “1” would be entered into column 20 of the first row of computer memory space. (A “2” would be entered if the respondent answered “No”) Similarly a “1” or a “2” or a “3” would be entered into column 40 of the first row, depending on how the first respondent answered the multiple choice question regarding where the car was made. If the first respondent reported driving 22,000 miles last year, a “22” would be entered into columns 60 and 61 of the first row of computer memory space. (If the respondent drives only 6,000 miles last year, a “06” would be entered into columns 60 and 61).

This procedure would be continued for all questions on the questionnaire until the coded data fro the first respondent had been entered into the first row of computer memory space. The procedure would then be repeated for the second respondent using the second row and for third respondent using the third row, and so on.

Data entry is likely to become more efficient in the future as new technologies become available.

Computers tapes:

Computer tapes of data are very similar to data stored in computer memory space. Readers can think of a computer tape of data as a tape constructed by attaching the second row of data from a computer memory space to the end of first row from the same computer memory space. The third row of data from the same computer memory space is attached to the end of the second row of data, and so on.