REACTION-TIME AND MOVEMENT TIME Task Description The person being tested will stand stationary on one of the switch mats. React to the illumination of the light, move as quickly as possible, and contact the second switch mat. Record reaction-time and movement time Complete 5 trials Calculate the means for the 5 trials and record the values on the master score sheet. Make sure to also record “1” for male and “2” for female on the master score sheet. Reaction-Time Trial 1______ Trial 2______ Trial 3______ Trial 4______ Trial 5______ Mean_______ Movement Time Trial 1______ Trial 2______ Trial 3______ Trial 4______ Trial 5______ Mean_______ Statistical Analysis of Data Reaction-time and movement time scores will be compiled for all 4 lab sections and e- mailed to you in an Excel file so that you can complete the following statistical analysis. You will also be e-mailed a recent article (Der & Deary, 2006) that examined sex and age-related differences in reaction-time. 1. Follow the procedures from the first lab to calculate a correlation between reaction-time and movement time. Use “RT” and “MT” in the Name column. 2. A t-test for independent groups is used when the same variable has been measured in two independent groups and you want to know whether the difference between group means is statistically significant. "Independent groups" means that the groups have different people in them and that the people in the different groups have not been matched or paired in any way. Calculate a t-test to determine if males and females demonstrate significant differences on reaction-time Open another SPSS file by clicking on File, New, and Data Click on Variable View tab In the Name column type in “RT” and “Sex” In the “Sex” row click on the Values box In the dialogue box type “1” in value box and “Male” in the label box and click on Add Then type “2” in the value box and “Female’ in the label box and click on Add Click on OK when finished Click on Data View Copy and paste the scores from the Excel file into the appropriate columns Click on Analyze, Compare Means, and Independent Samples T-Test. Now, move RT into the Test Variable field. Move Sex into the Grouping Variable field. You will notice that there are question marks in the parentheses following your independent variable in the Grouping Variable field. This is because you need to define the particular groups that you want to compare. To do so, click on Define Groups, and indicate the numeric values that each group represents. In this case, you will want to put a "1" in the field labeled Group 1 and a "2" in the field labeled Group 2. Once you have done this, click on Continue. Click on OK to run the t-test analysis Interpreting the Output from Independent Samples t-test The first table lists the number of participants (N), mean, standard deviation, and standard error of the mean for both of your groups. The second table initially presents you with an F-test (Levene's test for equality of variances) that evaluates the basic assumption of the t-test that the variances of the two groups are approximately equal (homogeneity of variance). If the F value reported here is very high and the significance level is very low--usually lower than .05 or .01), then the assumption of homogeneity of variance has been violated. If this is the case, you should use the t-test in the lower half of the table, whereas if you have not violated the homogeneity assumption, you should use the t-test in the upper half of the table. If the value in the Sig. (2-tailed) column after the t-test column is ≤ .05, then there are significant differences in males and females. Click, copy, and paste the Independent Samples t-test box into the Word document you will be handing in. Questions 1. Is the relationship between reaction-time and movement time significant? 2. What percentage of variability in movement time can be accounted for by variability in reaction-time? 3. Is there a significant difference between males and females on reaction-time? 4. Review the Der and Deary (2006) article before answering the following questions: Are our lab results regarding male and female differences in reaction-time consistent with the findings of Der and Deary? Explain your answer. What kind of age-related differences in reaction-time did Der and Deary report? What are some of the potential real-life consequences for the age-related changes in reaction-time? Why might these age-related changes in reaction time be even more significant for women? Bonus: What factors do you think might decrease the age-related changes in reaction- time? Find one supporting reference.