Digit cancellation

Another test requiring focused attention is digit or letter cancellation, in which subjects mark through a certain numeral in a page of random numbers or a certain letter in a page of text or random letters. The typical duration of cancellation tests is 1 to 2 min. Two studies reported that diazepam (10 or 15 mg)157 and lorazepam (1 and 2 mg)124 impaired digit cancellation performance. Interestingly, Brown et al.157 found that impaired focused attention was not correlated with the ability to encode associative information. These studies confirm numerous previous studies that reported benzodiazepine-induced decrements in cancellation tests.7... 

Step 4 Check that you have cancelled the units correctly. Also check that the answer seems reasonable, and that the significant digits are correct. 

French-St.George et ah, 1993] French-St.George, Wood, M., and Engebretson, A. (1993). Behavioral assessment of adaptive feedback cancellation in a digital hearing aid. J. Rehab. Res. andDevel., 30 17-25. 

Numbers in proper scientific notation have only one digit in front of the decimal place. Can you convert 12.5 x 10 3 into proper form You have to move the decimal point one place to the left, but does the exponent increase or decrease Is the correct answer 1.25 x 10-4 or 1.25 x 10-2 Rather than memorize a rule, think of it this way. You want your answer to be equal to the initial number. So, if you DECREASE 12.5 to 1.25, wouldn t you need to INCREASE the exponent to cancel out this change So, the correct answer is 1.25 x 10-2. 

Digit symbol substitution task symbol cancellation task IV 0.5 mg/kg/h... 

Substitute the known quantities into the simplified relations and perform the calculations to determine the unknowns. Fay particular attention to the units and unit cancellations, and remember that a dimensional quantity without a unit is meaningle,s.s. Also, don t give a false implication of high precision by copying all the digits from the calculator—round the re.sults to an appropriate number of significant digits (see p. 39). 

Once again, the order that you place down the conversion factors doesn t matter. What is important is that you were able to cross-cancel the units that you didn t want and that you got the same final answer. Did you remember to round your answer to 2 significant digits We rounded that way because we started off with 2 significant digits in the problem. 

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