As adults get older, their lives may become increasingly sedentary. Given concerns about physical and psychological problems associated with a lack of physical activity, one study investigated whether some office tasks such as typing, working on a computer, and reading may be performed at a satisfactory level while walking on a treadmill rather than sitting (John, Bassett, Thompson, Fairbrother, & Baldwin, 2009). One part of the study involved having 20 adults take a typing test two times: once while sitting at a desk and once while walking on a treadmill. The average number of words per minute (WPM) typed correctly for the two conditions was as follows: sitting (M = 40.20, s = 10.20) and treadmill (M = 36.90, s = 11.10). Furthermore, the researchers reported a mean difference score (X̅_D) of 3.30 and a standard deviation of the difference scores (s_D̅) of 4.70.

Test the difference in typing speed for the two conditions.

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a. State the null and alternative hypotheses (Ho and H). b. Make a decision about the null hypothesis. (1) Calculate the degrees of freedom (df). (2) For a = .05 (two-tailed), identify the critical values and state a decision rule. (3) Calculate a value for the t-test for dependent means. (4) Make a decision whether to reject the null hypothesis. (5) Determine the level of significance. c. Draw a conclusion from the analysis. d. What conclusions might the researchers draw regarding whether the task of typing may be performed at a satisfactory level while walking on a treadmill rather than sitting?